Contents

Editor: Ron Quinney (LES 1.5.4) Room 301, Editorial 203 High Holborn No noise is good noise- Telcare 1 LONDON WC1V 7BU Telex Plus 4 01-432 2806 Re-program your memory fast 6 Maintenance News Transverse-screen cables for digital transmission 7 New TIPs 8 Quality in the field 10 Mini computer maintenance in BT Newcastle 12 The TXD maintenance organisation 13 TXE4: Performance update 15 N NCC review 1968-1984 19 Cellular radio 20 Blinded by the light 21 Letter 25 National Networks: Maintenance News aims to provide a medium trunk services- maintenance 26 for two-way communication between maintenance Electronic component engineers throughout British Telecom. If you want Fast Response Service- FRS 29 to write about anything you may have seen in The Materials and Maintenance News, or indeed, about any Components Centre (MCC) 31 maintenance topic, send your letter to: The Editor, Stop press 31 Maintenance News, Room 301, 203 High Holborn, London WC1V ?BU. Say what you like, but the Editor may tone comments down if he decides to publish. Do please give your full address.

Produced by Local Communications Services Editorial No noise is good noise­ Teleare

There are two reasons for giving by Roger Sutton LES 4.2.1 Causes of noise Maintenance News a facelift in silver this Noise is not a new problem. Even so, A special study was camed out to determine time. Firstly, in celebration of issue number transmission difficulty is still the main the main causes of noise in the network and 25 and, secondly, to act as a marker on your cause of concern to customers using the to propose remedial action. Many bookshelf in the otherwise white-edged automatic telephone service. BT has investigations had been carried out in the display of back numbers I taken a fresh look at the problem so that past, but all had concentrated on a specific I make no apology for plugging "Repair remedial action could be started to part of the network in isolation from both the Care", following the mailing to all Area improve noise and transmission rest of the network and customer experience managers during September of a new performance. The most important aspect of this latest study brochure bearing that title. The brochure looked at the network as a whole and related describes the kind of services available from Telcare the problem to customer opinion. The British Telecom's 58 Area Repair Centres BT introduced Telcare (TELecom Customer investigation team visited customers who had (ARCs). Between them, they dealt with more Attitude REsearch) to assist in its drive to reported noise faults to a Repa1r Service than 200,000 electronic units last year One improve service quality and to tailor 1ts Control (RSC). Detailed investigation was of their more important tasks, as BT enters services more closely to meet customers' made of each customer's complaint, using the new era of accountability to its requirements. Telcare is a system of monthly, diagnostic questions, test calls and some customers, is to maintain quality. Area Repair nationwide telephone surveys with computer purpose-designed testing aids. Any noise Centre managers wiil be learning more of this assistance. To ensure complete impartiality encountered was recorded, measured and 1ts during the coming months as the new this task is carried out by external research source traced. standards of quality are implemented Les agencies. They use trained Interviewers and Waller's article in this issue, "Quality in the conduct over 1.5 million interviews nationally Results Field", introduces us to some aspects of this a year. Interviewers ask for customers' Not surprisingly, the team proved that topical subject. perceptions of one of four main reproducing and locating no1se faults­ Ron Quinney telecommunications activities Provision of particularly intermittent ones- was very Editor Service, Repair Service, Telephone Billing difficult and was not aided by existing test and Automatic Service. equipment and procedures Figure 1 shows In the Automatic Service survey, a random the team's findings as to the causes of noise sample of customers was asked a number of and compares them with the results recorded questions regarding their last telephone call. by the same RSC in the preceding month. Results showed that noise and poor The main points to note are transmission were the main causes of • the lower percentage of faults proved on to customer difficulty- noise being the most the customer's apparatus (45% against significant factor. 68%) - F1gure 1 Causes of noise Exchange and network faults apparatus in the period before an These results demonstrate the difficulty field investigation. This is quite understandable staff have in proving faults into the exchange and has some public relations benefits. But a and beyond. The team found that the only problem arises when this action is recorded effective way of achieving this was by as the clear for the fault, often leading to a following new procedures and using specially repeat complaint from the customer. It designed testing aids. It is particularly means too, that the business is planned on important to locate and clear such faults as false statistics. The new procedures do not they can each affect many customers. One preclude the changing of transmitters- in of the faults found during the investigation fact, carbon granule transmitters are provides a good example -a customer had replaced by electronic types on all noise or been complaining of noise for at least six transmission complaints. months and five unsuccessful visits had already been made by BT engineers. The Right when tested (RWT) clears cause of this fault was a faulty clock card on Staff have a natural reluctance to record a major 24-channel PCM route which 'RWT', preferring to demonstrate that they affected several channels of the system have found a fault. This is shown by the lower Clearly this fault must have affected a very number of RWT 'clears' recorded in the large number of other customers during this period before an investigation. Analysis of period and would have generated many other fault reports from several Areas indicates Figures in brackets are unsolved complaints. The affect on customer that this can lead to a repeat fault rate of as for the previous month opinion caused by this type of fault is only too much as 27% for noise and transmission at one of the RSC's visited obvious. reports at some RSCs. • the higher percentage of faults proved into the exchange and network (21% against Customer apparatus faults Distant end faults 7%- a f1gure that is well above the Because of the difficulty- outlined above- of Six per cent of the faults were proved to be at national average of 3%) proving exchange and network faults, there 1s the distant end, something that is very rarely, • the higher percentage of faults proved a tendency for the Customer Apparatus and if ever, considered or proved at present. An Right When Tested (RWT) (16% against Line (CA & L) engineers to change the example would be that of a customer who 9%) telephone transmitter if no other fault is regularly called one number and often The results showed clearly that the readily apparent. This tendency is indicated experienced noisy calls. Because the fault carbon granule transmitter was the single by the significantly higher percentage of could have been at either end of the mam cause of no1se. 'clears' recorded against the customer's connection, it would only be by chance that 2 the customer with the fault would be the first • make test calls to non-metering 'quiet' lines the noise and transmission performance at one to complain. and/or distant customers those exchanges • introduce a minimum procedure for CA&L • several junction faults were identified, each Co-operation engineers to assist them in the difficult task affecting many customers. In one instance It was found that there was a general lack of of ·proving' noise and transmission faults all 30 channels of a PCM system were co-operation between exchange staff and • set up special teams, Noise Action Groups found to be faulty which is likely to have CA&L staff. To ensure that a noise or (NAGs), for handling the more difficult faults affected many thousands of customers transmission fault is correctly localised, the • accelerate the replacement of carbon before eventually being located line needs to be split at the MDF, so it is granule transmitters • a reduction in the number of written essential for exchange staff to fully co­ • use specialised maintenance aids for the complaints and Telcare Area referrals operate with CA & L engineers tracing location and clearance of noise and • an increase in job satisfaction. customer complaints. Such co-operation transmission faults As a result of the experience gained, needs to be immediate to maintain a good • keep adequate records to allow 'blackspot modified procedures were issued nationally public image. A 'line splitting' box- known as analysis' (see MN 21). in April 1984. Most Areas have adopted them, an Exchange Interface Unit, has been or are in the process of doing so. developed to simplify this task and to hold an Pilot area results already established exchange connection. The Action Plan was issued nationally in Now it's up to us This unit should be widely available soon. October 1983 and the first four Areas to The need to improve our noise and Another important discovery was finding adopt it were closely monitored. The results transmission performance, and our image at whole verticals of unsoldered new work on from these Areas over a four month period this time of liberalisation, competition and MDFs- and these were not wire wrapped confi~med the earlier results and also showed privatisation, has been highlighted by the joints! It was also found that the Tele 282- the following benefits: Telcare results. The new procedures and which was designed for exchange use only­ • the number of noise and transmission Noise Action Groups have proved to be a is unsuitable for localis1ng noise faults in the reports to the RSCs was significantly tried-and-tested method of achieving these field. reduced aims. But the ultimate success of this drive • the number of repeat noise and will depend on the degree of commitment Plan of Action transmission faults was reduced and dedication of the maintenance engineer. The Investigation showed that BT's resources • a reduction in the number of needless (01-432 2337) needed to be directed more effectively if the customer visits situation was to improve. The main points • the NAGs identified several particularly bad resulting from the Action Plan are to: exchanges. The evidence they were able to • obtain customer cooperation for diagnostic provide enabled the local manager to use tests his resources most effectively to improve 3 Tele~ Plus - the store-and-forward faeilit~ for tele~ eustonaers by Fred de Boise BTI/182.3.2 possible- single address • number of output message attempts is Although the national Telex service was first multi-address, adjustable for different error conditions, offered to the public in 1932, it was not until pre-recorded address lists (PRA), • adjustable time interval between output 1978- 46 years later- that a computerised and mixed addresses and PRA. attempts, Stored Program Controlled (SPC) telex A PRA list enables each customer to store • optional automatic advice of delivery exchange was opened in London's St up to 100 telex UK/International addresses on • journal of information on delivery or non­ Botolph's International Gateway. Once a service computer list. To telex each number delivery. established, thought was given to providing on his PRA list, a customer sends his customers with an extra facility- that of confidential access code, together with the Pre-Recorded Information (PRI) depositing their telex messages for automatic message to be sent, to Telex Plus. That PRI is stored on the Telex Plus system and is delivery, or making repeated attempts to message is then sent automatically to all the available to customers at any time. PRis are deliver them. An important feature would be numbers on his PRA list. A customer may currently used to provide service information advising the customer whether or not the maintain any number of PRA lists, but any and up to five can be stored on the system. delivery had been successful. one message can be sent to a maximum of After a small-scale trial, it was decided to only 10 PRA lists. o System outline- the functions of the incorporate this feature in a second SPC Reference information returned for each various components in the Telex Plus system telex exchange installed at Keybridge message, includes a unique message are explained with reference to Figure 1: International Gateway. This feature- known reference number, and a date and time Bus to Packet Adapter (BPA) as the 'Store-and-Forward' unit (SFU)- was reference. • sets up incoming calls to the Store and ready for service in 1983. An enhanced Delivery advice information gives advice of Forward (S&F) units version of the SFU, which has been called non-delivery or delivery automatically. • sets up S & F outgoing calls to the basic the "Telex Plus" service by BTinternational, switch over the Inter-Unit Bus (IUB) will be ready soon. BT's facilities • provides transmission-rate control The facilities offered to BT include: processing on incoming and outgoing S&F Telex Plus facilities • access barring for each incoming trunk calls The protocol for inputting messages includes group, • transfers data characters on a call basis to a 'conversational' call set-up procedure • inhibition of a transmission on a trunk group and from the IUB during which the customer can request when a pre-determined occupancy • assembles and disassembles data packets 'HELP'. A message can then be input either threshold is reached, of Telex Multiplexed Format (TMF) from the teleprinter keyboard, from paper­ • inhibition of output message transmission characters tape, or memory, and is delivered as soon as for pre-determined periods by using special • manages and routes database request possible after it has been input to the system. 'destination' country codes (known as packets from S& F units to the appropriate Four types of address specifications are CCITI F69 codes), front-end queues, and sends them to the 4 Accounting PRA!PRI IUB =Inter Unit Bus data data FE= Front-End processor Operator system DCU = Disk Control Unit Basic switch G MTU =Mag Tape Unit LP =Line Printer Basic switch F SFU =Store and Forward Units Basic switch E PRA =Pre-Recorded Address lists PRI =Pre-Recorded Information BP =Batch Processor • compile accounting records for each Telex successful or unsuccessful outgoing call basic and sends this to the front-end switch u "D" • compileS& F statistics which are output to the front-end. B 1/C&O/G Telex trunks Front-end processor • loads the BPA and basic switch subsystems with software • polls for accounting, MRO messages, ---. statistics, journal records and database Bus Message Disk 1----1 Packet Storage modules requests from the basic switch subsystems Adapter (300 Megabyte) and the BPA ___j • passes broadcast date/time and unit identification messages to all basic switches and the BPA • routes MRO messages to the appropriate machines Figure 1 - Telex Plus block diagram • queues database requests to appropriate tasks and disk storage module (DSM) front-ends when the queues are polled, and • queue messages for output on normal or response to the BPA • passes various records, statistics and deferred queues with delivery information • writes journal records and accounting maintenance read out (MRO) fault for each caller address for the message records to the appropriate 80 Megabyte messages from the S& F units to the front­ • set up outgoing calls for messages DSM. end, as well as passing control date/time secured, monitors for the end of all information and unit identity to the S&F addresses for the message, then sets up Batch processor units. advice of delivery/non-delivery for that • produces accounting tapes from the disk particular message and queues this for records Store and forward units (S&F) output • handles operator database update requests • accept incoming calls, validate incoming • compile journal records for each message for the PRA and PRI data protocol and secure incoming messages on when the last advice of delivery/non­ • handles auditing of front-end A and B the 300 Megabyte moving-head disks delivery has been sent database DSMs to ensure system integrity.-. 5 Operators can compare disks and copy output on the printer which can be related to disks the lookup table. Re-progratn • produces database tape back-ups for disk No difficulties are expected with the 'images' maintenance procedures on the new your tnetnor~ • allows operators to do journal searches at equipment, as they closely follow those customers' request, for advice of messages already in use for the basic telex switch. To • disk back-up tapes can restore database ensure secure fault handling, fault reports fast PRA/PRI information for the 80 Megabyte contain date, time. and ca!l reference DSM. numbers. by Graham McLachlan LES1.5.3 ~JMaintenance- Magnetic Disk Unit- apart Summary of system Programmable memory devices are used in from normal preventive maintenance, such For interest, the main dimensions of the many modern electronic systems to allow the as keeping filters and magnetic heads clean, system are- facilities offered by a system to be easily tests are made with a Field Test Unit (FTU) • maximum message size, 8000 characters upgraded or modified. Using this flexible (TB304B). This checks all functions on the approach, BT has the ability to meet (about 20 minutes. or 120 lines of text) disk unit, including read, write, head customers' needs for additional system • multi-address messages: maximum of 100 alignment, and so on. The FTU is an off-line addresses per message facilities quickly, and to keep ahead in tester, meaning that the drive cannot be • maximum of 10 PRA codes per message today's competitive markets. selected or used while tests are being The use of these devices in equipment • maximum of 100 addresses per PRA performed with the FTU. supplied by BT. requires us to be able to re­ • maximum of 100 authorised users Magnetic Tape Unit- TheSE Labs tape program them when necessary. In the past (selection codes) per PRA unit has built-in micro-diagnostics, with 99 • absolute maximum number of addresses this has been done either by removing switch-selected test programs. An indicator per message is 1090 (1 0 PRAs with 100 devices from the printed wiring board (PWB) gives a 'run', 'pass', or 'fail' indication. In the and then re-programming, or re-programming addresses. plus 90 single addresses) event of a fail, an indication is also given by them using a purpose-built board • maximum of 14,000 PRAs means of an error code which can be related programmer. It is not always practical to • maximum of 5 PRis to a program listing. equip Area Repair Centres (ARC's) with • journal capacity of 7 days S & F Processor- this is tested using a test dedicated board programming systems and, • storage capacity for 88,000 messages and verify (T & V) diagnostic program given the increasing usage of this type of (average message of 1200 characters) associated with the system. The main PWB, BT is investigating advances in board • BPA will handle 11 ,000 calls per hour purpose is to test the various items of programming systems to cope with future (average message of 1200 characters) hardware comprising the Central Processor growth and technological advances. • each SFU will handle 5500 input calls per Unit (CPU) and peripherals. In all cases the Against this background, an order has hour (average message of 1200 characters) T & V programs are resident on the system (01-936 3322) been placed for what has been described as disk and need not be loaded from paper tape. the world's first universal EPROM (erasable The processor T & V is designed to programmable read only memory) board thoroughly exercise the CPU logical, shift, programming system This system was and skip instructions in differing modes of launched recently in the UK by Data 1/0, and operation. If aT & V test fails, a number is will be evaluated for use in ARCs. 6 Transverse-sereen eallles for digital transnaission by lan Dufour LLS2.1 attenuation, near-end crosstalk (NEXT) and Transverse-screen cables were introduced far-end crosstalk (FEXT). All of these were specifically for carrying 2Mbit/s digital line interactive, but the DC resistance was of systems. Their origin lies in two decisions prime importance because of power-feeding The board programmer, known as the taken in the mid-1970s- limitations. The remainder affected the 156A, will be allocated to an ARC with the • An international decision to adopt a 2M bills maximum distance achievable between facilities to provide a rapid system software and 30 channel hierarchy, whereas BT had regenerators. It is worth noting that the update service for local exchange and call been using 1.5Mbit/s and 24 channels. principal factors affecting the cable connect systems, such as System X, UXD5, • The decision by BT to adopt digital parameters are- TXE4A and Monarch. switching (System X), which affected overall • the diameter of the copper conductor The new board programmer will have 32 system economics to such an extent that which affects the DC resistance; times the capacity of current purpose-built digital transmission between exchanges • the attenuation, influenced by the board programmers It is universal in as became the norm. diameters of, and rations between, the much as it can handle the types of work The result was that digital transmission conductor and the insulation; performed by all existing programmers, at the requirements at the new- and largely untried • NEXT, influenced by the screen design; same time providing flexibility to meet future - 2Mbit/s rate escalated beyond anything • FEXT, influenced by the screen design, the needs. previously foreseen. At the time it was layout and twist length of the pairs. (A more If the evaluation is successful the system expected that the first few years growth in detailed technical explanation can be found will be installed in strategically-located ARCs the junction network could be contained on in British Telecommunications Engineering, around the country to provide a fast, the existing metallic-pair (quad) CJ cables Vol 1, January 1983.) nationwide, software update service. with the use of optical fibre systems (OFS) in (01-432 2818) Aluminium foil the later years. It is now a matter of history Over and above the technical requirements, that the 2M bills systems met with difficulties was a need to have a cable which could be which substantially increased the cost of produced in quantity at short notice by the using existing cables, and the economics British cable industry. The end result was a were unfavourable to the early introduction of cable combining a simple pair structure, OFS in the junction area. The resulting gap in common in most respects to the widely­ the planners 'tool-box' was filled by produced 0.6mm local distribution cable, with transverse-screen cable. a simple aluminium-foil screen used to separate Design the two directions of digital transmission. The design of transverse-screen cable had to balance the requirements of a number of Benefits characteristics, namely: DC resistance, Apart from being a low-cost cable design, - 7 transverse-screen cables have the added advantage of being simple to install using New TIPs existing practices and techniques. Many of these installation benefits are passed on to by lain Mcintyre LCS/OPS1.2 measured- by means of a new TIP subsequent maintenance operations- TIPs (Telecomms Improvement Plans) were (TIP1A)- but it will also refer to ECs per • Long length cabling (typically 500m and up introduced in 1966. An essential part of these annum. There is also a relatively minor to 1DOOm) means less JOints to make and plans is setting invidividual targets for change to TIP2 in that carried forward faults maintain are now only counted once. • Straight joints- pair 1 to pair 1, pair 2 to Regions, Areas and often for individual units pair 2 and so on- means no complicated in Areas. The level at which the targets are Most of the changes are more fundamental. set takes account of differences and however, and have been made to ensure that JOinting schedules and subsequent records problems facing particular parts of the our TIPs reflect more accurately the service • Shrink-down sheath closures give a first­ class long-lasting seal in minimum time country, but it has always been an objective as it is seen by the customer. For example. • Limited testing minimises acceptance time that Tl Ps should be challenging and just TIPs52 and 53 measure the whole path of a both initially and after faults 'within reach' if an effort is made to achieve dialled call, whereas the superseded TIPs3 them. As well as the special considerations and 4 measured only from 1st selectors or • Limited range of stores items and manpower 1st code selectors on local calls, and from skills means better chance of reducing affecting Areas, there is a continuing need to the register access relay set on STD calls. installation times and fault outage times. improve the quality of the service we are giving to our customers throughout the UK. This meant that failures to obtain dialling Applications This need to improve is the major factor tone, or to get access to the GSC. were not Transverse-screen cables were introduced which influences targets. recorded. It should be noted that TIPs52 and for junction network applications but they are 53 have now been formally split into their now increasingly to be found in the local Changes plant defect and plant engaged elements, network. Here they are used for 2Mbit/s From April 1984 a number of TIPs have had TIP52A, 528. 53A and 538 respectively private circuits- MegaStream for example­ their definition changed or have been In recent years provision-of-service targets and, soon, for 2Mbit/s links from digital PBXs replaced by something new. These changes have been revised at intervals by shortening to digital exchanges. are listed in the table. This article explains the the target timescales. Tl Ps 19, 20A and 208 Although transverse-screen cables have reasoning behind the changes. are not strictly new TIPs, but the changes in been a vital link in the digitalisation program Some of the changes were needed simply definition which have taken place make them there is now considerable hope that optical to tidy up definitions to take account of the more testing. Inevitably this will bring BT's fibre systems will be economical on quite a change in BT's monopoly status. For performance in providing service, up to wide scale in the junction network. Optical example, TIP1 is now 'faults per exchange customers' expectations cables could well displace transverse-screen connection (EC) per annum' instead of 'fault cables for new provision within a couple of reports per station per annum'. With plug-in Private circuits years or so. For local applications the telephones, customers can change telephone Business customers, not surprisingly. place transition will take rather longer but there is a instruments without involving BT and there is great importance on speedy repairs to private fair chance that it will happen. no possibility of keeping track of the number circuits (PCs) and it became obv1ous that the (0 1·35 7 3354) Editor's note. Optical fibre systems of telephone stations in use in future. For the TIP2A definition 'percentage of faults cleared wt/1 be the subject of a future article. sake of continuity, fault reports will still be by the end of the next working day· was not 8 good enough. It has been replaced by 3 new measures: TIP42- 'PC faults cleared in 4 Definition TIP working hours' TIP43- 'PC faults cleared in Old New 12 working hours' and TIP44- 'percentage repeat faults'. These TIPs show how Fault reports per station per annum Faults per EC per annum important it is to effect speedy repairs, but it should be noted that if there is a temptation 1A Fault reports per EC per annum to make temporary or inadequate repairs in 2 Fault reports cleared by end of next Fault reports cleared by end of next the cause of speed, the result could be a working day (carried forward faults working day (carried forward faults good TIP42 but a poor TIP44! counted each day until cleared) count once only

Telcare 6 Repair service PCA25 As part of the drive to make all BT staff 2A PC faults cleared by end of next Replaced by TIP42 customer orientated, targets have also been working day set, for the first time, for overall Telcare measures. Customers in all Areas are asked 3&4 Calls failed due to BT Replaced by TIPs 52A, 52B each month what they think of the service (local and STD) 53A and 53B they have recently had from BT. Three 42 PC faults cleared in 4 working hours hundred interviews are undertaken using the latest computer-aided telephone interviewing 43 PC faults cleared in 12 working hours techniques, in each of the following categories- 44 PC % repeat faults per month • Provision of Service: business 19 Res orders completed in 12 working Res orders completed in 8 working • Provision of Service: residential days or customer's later required by days or CLD • Auto service: local date (CLD) • Auto service: trunk • Repairs: business 20A Bus small orders completed in 8 Bus small orders completed in 6 • Repairs: residential working days or CLD working days or CLD • Billing Telcare New survey As mentioned in the article by Roger Sutton 'No noise is good noise', the preliminary Res residential customers EC exchange connection study of the Telcare results has shown some Bus business customers PC private circuit major additional causes of dissatisfaction. CLD customer's later PCA 25 = percentage of calls answered in For example, too many customers say that requirement date 25 seconds they had difficulty in trying to contact BT to 9 Quality Quality' of service report a fault. To keep this important aspect in the field of the service under review and to stimulate t t improvement, TIP6 has been introduced. It Measured by Measured by by Les Waller OPS2.2.5 measures the percentage of calls answered Telcare TIPs What is Quality? in 25 seconds by the repair service. (Subjective) (Objective) Quality can be defined as having been achieved when the product or service does Comparisons what the customer expects it to do and what But, is it realistic to react to our customers' I Review of I BT says it will do. Essentially quality means recollections of the service they got? Won't results 'fitness for purpose' or 'conformance to a set different people have different standards and standard'. expectations? Figure 1 shows the situation t we would normally expect to find. If the Does BT have a Quality problem? service is good, then the TIP measures Any required Surveys of completed work, completed corrective (which are objective, that is they can be action records and completed Advice Notes- allied measured with reasonable accuracy as in taken to discussions with staff at all levels- have say TIP2 'percentage fault reports cleared by highlighted the need to improve quality the end of the next working day') and the t standards over a wide area involving Sales, Telcare measures (which are subjective, that Planning and Works as well as Maintenance Service is we record whether the customer is improves activities. satisfied or dissatisfied) will be good. If the service is bad, then we would expect both to I Who is to blame for Poor Quality? be bad. In practice we are finding that, Traditionally maintenance staff tend to blame generally, the best Areas as measured by • poor standard of construction work TIPs also have the best Telcare results. • bad planning Telcare results can also be used to check • inadequate techniques whether the TIP targets as set are in line with also possible to determine what the average • 'fire brigade' maintenance policy the standard of service which our customers fault clearance time would need to be in • inadequate supervision expect. For instance, a proportion of order to reduce the level of dissatisfaction to • poor quality stores customers are dissatisfied with the time it a figure which would give rise to few Field surveys have shown the main reasons takes BT to clear a fault. Telcare results have complaints. This sort of analysis is useful in to be: been analysed to show what length of time­ helping to work out our priorities as we move • lack of initial or refresher training from reporting a fault to completion of repair into the era of competition, for we will only • inadequate supervision. -they would be satisfied with. This analysis succeed if we can provide the service that showed that business customers are less our customers want, at a realistic price. What is LCS doing to improve quality? easily satisfied than residential ones. It was (01-432 4310) LCS Headquarters has set up a Quality 10 Council and LCS Areas have appointed Where are quality systems being action where necessary. Quality Managers to gtve added impetus to applied? First line supervisors also have a vital role the drive to improve quality throughout LCS. Quality checking systems have been to play. The recently compiled LCS Quality Manual designed to cover work in the field and in The regular, disciplined, use of checklists states that to improve quality in the field there telephone exchanges. with the emphasis equally on quality as well must also be: In the maintenance field they already as quantity of work, provides a convenient • a dedicated quality policy cover the work of Customer Apparatus and and effective monitoring system which • quality management disciplines Line (CA&L) staff, maintenance jointers and enables weaknesses in both plant and • detailed qual tty plans. faultsman jointers. For internal staff they techniques to be rapidly identified. Don't To achieve this improvement LCS HQ is cover TXE4 night routining. Further systems forget the value of feedback. A good quality providing Area managers and staff with the are being designed and these will cover the job is just as worthy of praise as a poor means of achieving the required ·quality majority of outstanding major fields of quality job is of criticism. standards' by introducing detailed Quality activity. Finally, field staff themselves. The need for Plans involving the use of specially designed For an up-to-date list of Quality Control 'pride of workmanship' was never greater checklists. Projects see Prestel, commencing at page than in the new competitive environment. In essence these take the form of: 540161. Checklists are there to make sure you don't • a quality control system whereby first line overlook important items such as supervisors use a formalised inspection What part can I play? comprehensive testing and accurate records. procedure to check samples of completed To achieve success from any of the After all, the flight deck crew of a Jumbo jet work done by their staff. The staff too are previously mentioned systems, staff at all use a checklist, so why shouldn't you? helped, not only by receiving objective leve!s must be totally committed to quality. The opportunity cost of a poor quality job supervision and guidance, but also by being Quality affects everyone's job in differing can be seen as the expense needed to issued with a concise summary of the ways. During the National Quality campaign correct the job, or, put another way, the cost standards of work required. the Prime Minister said "Responsibility for of quality can be seen as the expense of • a monitoring system enabling higher achieving quality rests squarely with top doing things wrong. This applies equally to management to ensure that the quality management but everybody must recognise maintenance as to anyone else. control system is doing its job and that that quality is their business too". A slogan which has been adopted by problems identified are being acted upon at Area and District management must 'set us- and which we think should be foremost the appropriate level. the scene· by taking an active interest in in everyones mind- is 'do it once do it right'. • a management information system which quality of work not merely by looking at the If we all try and apply that to our daily work integrates quality control and monitoring 'slats' but also by regular, personal visits to the quality of work in BT must improve. procedures. see for themselves the quality of completed (0423 60781) work and by initiating appropriate remedial 11 Mini computer maintenance in BT Newcastle Figure 1 by Ken Sutcliffe BTNE/NT/E01 Computer mamtenance- stages tn organisation rece1ved thorough tra1n1ng covering repair of A report issued by BTHO in 1982 made Equipment the computer and two types of d1sk drive. To various recommendations to gu1de the 3rd L1ne support l_____ consolidate their training and build on their ....._--r---r-1_ __.I - manufacturer business towards the 1n-house maintenance ______expertise, the staff are based 1n the Area of its own computers. Newcastle Area- w1th ,_, Repair Centre where spare equipment has a population of s1x s1m1lar Alpha M1cro mini Repa1r been provided for this purpose. computers maintained by an outside agency depot at a h1gh cost- was 1n an 1deal position to (Area Repa1r Types of equipment take the in1t1ative. So we set about assessing Centre) The Alpha M1cro systems which the the feasibility of this type of venture­ Computer Service can presently maintain are- ass1sted by THO and RHO. Customer's • AM100 -2 board CPU using WD16 ch1p Following the study, a maintenance - prem1ses set philosophy was formulated wh1ch identified • AM100T -1 board CPU using WD16 chip the key factors to be satisfied for a viable Second line maintenance set computer repa1r organisation Th1s philosophy The 2nd line maintenance eng1neer 1s located • AM 1DOL- 1 board CPU us1ng MC 68000 has now been implemented in Newcastle 1n a repair depot. In Newcastle this IS the processor. Area. Area Repair Centre (ARC)- being eminently The operating system used is called AMOS. suited for the task. The eng1neer faults and Coupled to the min1 computers are d1sk Maintenance philosophy repa1rs plug-in un1ts down to component drives, and direct in-house repairs can be The overriding a1m of the computer level, carries out repairs to disk drives wh1ch made to CDC Hawk and Phoenix dr1ves. At mamtenance organisation is the rapid cannot be accomplished easily at a the present time Winchester-type drives have restoration of service both of computers and customer's premises, and also provides to be sub-contracted for repairs. peripherals, at an economic and realistic back-up to the 1st l1ne engineer for both Peripherals such as VDT's, printers and so cost. To th1s end, the procedure- illustrated software and hardware problems. on can also be maintained. in figure 1 -has been established. :J Third line support ARC equipment 'J First line maintenance This IS requested from the manufacturer if One advantage of basing the computer The 1st line maintenance engineer IS the 1st and 2nd line maintenance staff are service in the ARC is the use which can be expected to repair a broad range of computer unable to resolve the problem locally. made of existing tools and test equipment. and peripheral equipment using plug-in For example, wave soldering apparatus, logic replacement units held 1n a maintenance kit. lJTraining and signature analysers, and so on. But to Rout1ne maintenance and simple disk drive To carry out these tasks efficiently, the repair computer equipment efficiently, repa1rs are also within his domain. computer maintenance engineers have various items of specialised equipment have 12 been obtained. In this case- • spare system including disk drives TheTXD • spare plug-in units • special disk repair tools and repair aids • disk spares naaintenanee organisation • diagnostic tester • diagnostic software by Adrian Frame LES4.2.2. The problems • comprehensive documentation The introduction of System X local Stored Program Controlled (SPC) telephone • electro-static protection equipment. exchanges and digital junction switching exchanges, such as TXD, present a unique These are some of the major items which units (collectively called 'TXDs') will have set of problems to our maintenance have been obtained. a marked impact on maintenance organisation. Once established, the reliability Support and assistance by the computer activities. Here we look at the proposed of equipment using modern integrated manufacturer is acknowledged as a vital structure of the local maintenance circuits gives maintenance staff little factor in obtaining the repair tools and organisation (LMO) put forward by LCS opportunity to acquire and retain an in-depth equipment, and easing BT staff into this area Headquarters. While these proposals will knowledge of the system. Furthermore, the of work. be flexible enough to meet most complexity and diversity of the sub-systems situations, District managers may choose within a TXD makes it unlikely that anyone Encouraging results to adapt this structure, or adopt a could become truly 'expert' in more than a Newcastle Area has now received a seventh different policy, to suit local couple of sub-systems. A traditional Alpha Micro system to add to its circumstances. maintenance policy based on the philosophy maintenance commitment, and the early of on-site fault-finding to component level, results of the computer repair service are Objectives would require substantial investment in both encouraging (the agency contracts have only The objectives of the TXD local maintenance training and sophisticated test equipment. recently expired). Alpha Micro equipment is in organisation (LMO) are: The reliability of TXD will be such that this use in other parts of the business on systems • to minimise the degree to which faults level of expenditure could not be justified. such as CAME03, CIRAC and CAIRO and become service-affecting- by observation Indeed, when the fault is located, on-site this service will offer a viable alternative to of the exchange processor output, for board substitution and off-site repair will be agency maintenance. example the most cost effective maintenance method. • to speedily restore service to customers Future when a service-affecting fault occurs (and The solution The venture is considered as a stepping­ the system has not automatically The maintenance policy formulated by LCS stone towards profitable avenues of reconfigured to safeguard service) headquarters structures the TXD and maintenance, with the benefit of an increase • the economic and effective use of concentrates expertise in- in job opportunities. When sufficient expertise manpower and other resources, capable of • Operations and Maintenance Centres has been established from dealing with this being effective throughout the introduction (OM C) type of computer equipment, an expansion of of TXD and flexible enough to meet the • Operations and Maintenance Units (OMU) the computer repair service is envisaged. needs of today's competitive environment. As shown in Figure 1, an OMC is situated in a (0632 613268) telephone 'catchment' area at which, or through which, location various operational- 13 Figure 1: Typical relationship betweeen engineering support facilities. The OMU is the individual EMTOs. TXDs. OM Us and the OMC in an OMC focal point for the maintenance of all TXDs in The maintenance workload of all TXDs in catchment area. a defined geographical area. an OMUA- including OMC and OMU An OMC may have more than one OM U equipment- includes the maintenance duties connected to it. The first OMU- usually co­ in the OMU. So. wherever possible, EMTOs located with the OMC- is called the ·Main will share in the OMU duties on a rotational OM U ·, and the second and subsequent basis. OM Us are called 'Satellite OMUs'. An OMU -together with all the TXDs with which it is How will the TXD-LMO work? associated- is called an OMU Area (OMUA). As TXD penetration increases, there is likely (Len Strickland's article (MN 22) descnbes to be more than one OMU per OMC. All the OMC in more detail.) OM Us will be staffed during normal working Responsibility for the service given by the hours. But while there is low TXD penetration TXDs rests with the Engineering Maintenance in an OMUA, the OMU duty may include on­ Manager In Charge of the OMUA He is site maintenance of co-located TXD responsible for monitoring the service given equipment. or other system monitoring by all the TXDs in the OMUA and ensuring maintenance tasks. Areas will assess- and that maintenance and allied engineering periodically review- the need to staff an activities are executed in the most suitable OM U and whether to concentrate two or way. more OMUs into one. The size of the maintenance workforce Exchange alarms and automatic fault OMU operations and maintenance unit required to 'staff' an OM U is based on the report output are presented at both the TXD OMC operations and maintenance centre total number of TXD connexions in the and the OMU at all times. Monitoring of these TXD telephone exchange digital OMUA Allowances are given for any alarms and ouputs is carried out both at the and maintenance procedures are performed. travelling that may be necessary and other TXD and the OMU and, if the EMTO is in OMC users cover several operational activities performed by the OMUA staff. This attendance at the TXD, he will take the disciplines and are dispersed throughout the staff will be responsible to the Engineering initiative for appropriate action. When the catchment area. The OMC comprises a Maintenance Manager for the operation and EMTO is not in attendance. or for some other processor and its associated port switching maintenance of the OMUA as a whole. But, reason is not able to deal with the report, the hardware, modems and peripheral since the OMUA will comprise the workload responsibility for initiation of action rests with equipment. of more than one Exchange Maintenance the OMU. The OMU is an engineering base within an Technical Officer (EMTO), each OMUA may Where a TXD is co-located with its OMU, it OMC catchment area comprising a number be sub-divided into sections with the prime may be more effective for some of the 'on­ of visual display terminal and hard-copy responsibility for the maintenance of site man-machine interface (MMI)' activities printer work positions, together with other particular sections being allocated to to be done in the OMU. 14 TXE4: Perforltlanee update

When a fault occurs at a TXD and the by Peter Jones and Deryck Rogers EMTO is not in attendance, the OMU initiates LES4.3.1 • Mean Time Between Major Service Failures diagnostic action. After initial attention, if a In Maintenance News 22, Peter Jones (MTBF- average time between Major site visit is needed, the OMU contacts and discussed performance indicators and the Service Failures per exchange). advises the EMTO to attend the TXD performance improvements sought for concerned. On arrival at the TXD, the EMTO TXE4. Now he and Deryck Rogers report DA51: assumes responsibility for fault clearance. on the improvements that have been Figure 1 shows that we have made The OM U is the centre for fault records achieved, and examine the scope for considerable progress in improving the and documentation for the OM UA. It has greater achievements. exchange fault rate, TXE4 now being second facilities for carrying out in-depth analysis of only to Crossbar. But we know that customer problems and faults. As such, the OMU Our slice of the cake complaints are directly related to calling rate provides technical support to EMTOs when At the time of writing, there were 338 and, if that is taken into account, TXE4 would required. TXE4(RD)s and 27 TXE4As in service, with a show the best performance. Even so, there is In addition to the support facilities provided capacity of 3.7 million Exchange Connexions still room for improvement as can be seen at the OMU, LCS Headquarters have (ECs). TXE4s make up 6% of all exchanges from the distribution of A51 results shown in established a Maintenance Support Agency and serve 18% of all ECs. By 1990, a third of Figure 2. Those exchanges that are in the (MSA). The MSA is available 24 hours a day all our customers will be served by about 570 right-hand tail are not achieving anything like and acts as the primary interface between TXE4s. The system is also changing; we have the performance that the system is capable the District and the design, development and hybrid exchanges that are a mixture of of, even when calling rates are taken into support resources within the British Telecom TXE4A and TXE4(RD) control equipment, and account. So where can we get further and the manufacturers. facility changes brought about by improvements? Most of the faults are The OMU is the communication point for enhancements. These factors should ensure associated with customers' exchange all matters affecting the integrity of the that TXE4s will be around for a considerable equipment which includes the rather network as a whole- at all times- and for all time. unglamorous MDF. For various reasons, other matters concerning individual TXDs work carried out on the MDF fails to enjoy when the EMTO is not in attendance. Present Performance the high quality of workmanship enjoyed by It is hoped that the policy and organisation There are many ways of assessing exchange the rest of the exchange. Dry joints are still outlined in this article will meet service performance, the latest of which is Telcare our biggest problem. They not only give rise objectives while giving due regard to the (see 'New TIP's' in this issue). to poor A51 results but also generate noise problems peculiar to TXD and the needs of But TXE4 performance is judged by other faults that often go unreported, but are staff employed on maintenance duties. indicators, such as: reflected in Telcare results. (01-432 9027) • A51 Results: Line 27 Customer Reported Another aspect of A51 performance is that faults per EC per annum. This statistic was of Faults not Found (FNFs). We have found known as Line 28 until recently. that exchanges with few FNFs also enjoy • MAC: MS1 Own Exchange Plant Defects good co-operation with their Repair Service-+ 15 0.08 Figure 1: Exchange faults per EC per annum (A51: L27)

0 07 D as at MAY 1983 faults and inadequate records. Ill as at MAY 1984 Additional maintenance information on 0 06 MAC performance can be gleaned from Evening Session results. These are more important than Day Session results for those 0 05 exchanges that have their busy hour during the evening. 0.04 D Major Service Failures (MSF) The MTBF of TXE4 has improved from 14 0.03 ~ Exch months- early last year- to 30 months at ~ FNF present. However, it can be seen from ~ Exch common eqpt Figure 5 that we still have a long way to go. 0 02 ~ fault per EC The 50 year MTBF of TXS (strowger exchanges) is really the MTBF of the power Customers exch 0.01 supply, power distribution and tone eqpt fault per EC generators. It is very difficult to isolate a TXS including MDF other than 'failing' that equipment, because 0 ! of its distributed control. TXE4 can be more All TXS TXK TXE2 TXE4 directly compared with TXE2 and TXK1/3 because they are all common control Control (RSC) This leads to correctly counts. If we are to maintain and improve our systems. If MSFs caused by Working Party d1agnosed faults that reduce the number of lead, it is vital to eliminate 'own-goal' faults faults in TXE4 could be eliminated, we would FNFs and, consequently, reduces the amount such as forgetting to release an access h2ve an MTBF of nearly 20 years. This can of maintenance time wasted looking for faults circuit after tracing a MAC-held call. Figure 4 only be achieved by: that are not there. shows the distribution of TXE4 MAC MS1 PD • carefully following procedures, such as results for May 1984. It can be seen that over never removing a unit marked with a red MAC a quarter of all TXE4s had no MAC failures for triangle unless the necessary procedures The MAC results (MS1 PD) for June 1984 are that month. It can also be seen that there are have been followed shown in figure 3. They show that TXE4 is still some TXE4s that are out of line with the • doing work on sensitive parts of the now the clear front runner in MAC rest. Their poor performance is usually exchange during light traffic periods performance, and is well on course for its associated with poor quality extension work • taking particular care when doing System target of 0.15% by March 1985. The results and lack of attention to 'A' relays and coin­ Security Checks mean that, on average, TXE4s have less than and-fee check equipment (CFCs). This is (formerly known as Dormant Fault Checks) two MS1 PD faults per month so every fault often aggravated by poor documentation of • caring about the quality of the work done in 16 180 ...... ---..., Figure 2.· Distribution of Exchange faults per EC per annum (A51. L27)

160

140

120

100

80

60

40

20 ol___ _L __ ~----~---~~==~===L==~----~~~--~==~ 0-0019 0.020-0.039 0040-0059 0060-0079 0.080-0.099 1.000-1.199 1.200-1.399 1.400-1.599 1.600-1.799 > 0.200 your exchange- insulating your wrapping • A51- 0.025 (by end of March 1985) DMajor role tools would also help. • MAC MS1 Own Exchange Plant Defects TXE4 has a major role to play in providing It is interesting to note that the improved - 0.15% (by end of March 1985). service for our customers in the future. design of TXE4A has resulted in only one • MSF- MTBF fo 5 years (during 1984). Nationally, TXE4 is providing a better Design Deficiency being identified that Most exchanges have already achieved or service than any other major system but causes FNFs, as opposed to 27 in TXE4(RD). bettered the above targets With the some TXE4s still have room for improvement. Even so, both systems have the same MTBF. emphasis now on Quality, the above targets, Major service failures by careless action In other words, almost all of the MSFs that along with other performance indicators, will are our greatest weakness. have occurred in TXE4A were caused by be embraced by Area (District) Quality Plans, We cannot afford to be complacent if we working parties. taking into account local circumstances. are to maintain and improve our present Other facets of maintenance will be included performance. The future in the Quality Plans including the accuracy of (01-432 2457) n Future targets records and the importance of correctly The national TXE4 targets for the three main recording fault information as mentioned indicators are:- earlier. -17 1.2 - Figure 3· MAC MS1 0 wn exch ange pi ant defects June 84 50 Figure 5: Mean time between failures (MTBF) (years) 1.0 - 40 0.8 -

0.6 - 30

0.4 - 20 0.2 -

0 I I 10 TXS TXK TXE2 TXE4 TXD

100

Figure 4: Distribution of 314 Exchanges on MAC Sequence 1 PO for May 1984 TXS TXE2 TXK TXE4

80

60

40

20

0 0.1-0.2 1.0-1.1 2.0-2.1 0-0.1 0.2-0.3 2.1-2.2 18 National network eo-ordination eentre review !.968-!.984 by Jim Gipp NN!TS02.3.3 operated. Valve systems have not gone from performance parameters for new systems, in NCCs were set up in 1968 with a general the coaxial network and new growth IS with particular the growing digital network. The brief to monitor the performance of the digital systems. summaries draw managements' attention to whole telephony network by collecting Also during the period, although there has the sort of failures occurring in the network, data about major service failures. They been little change in the total number of so that appropriate remedial action can be are also responsible for controlling the exchanges, then they were all Strowger. taken. removal of plant from service for planned whereas now there are 63% TXS, 10% TXK Over the years these summaries have work, in such a way that service loss is and 27% TXE. contributed to an increased awareness on minimised by the use of the Service the part of maintenance engineers. Protection network (SPN). Also they keep FDM Performance watch on the performance of HF links and In 1968 the failure rate on main links was Network records trunks rented by the television authorities. more than 4 faults per 1OOOkm per annum. Our greatest difficulty has always been the When it opened, the National NCC with an average outage per failure of about 3 maintenance of accurate records of the comprised of 2 engineers and 1 CA. It had hours. These figures have improved to 1.5. make-up of the HF network in terms of plant grown to 8 engineers and 5 clerical staff and % hour respectively. The reduced failure and broadband use. These have improved by 1978. Now, with the introduction of rate has been brought about by the with the introduction of computers. and for microcomputing facilities, it has 6 introduction of transistorised transmission the digital network a system has been engineers and 3 clerical staff. equipment and the use of the more rugged developed usin'g Telecom Gold's Dialcom smaller bore coaxial cables having computers. This has enabled all NCCs, and continuous dielectric. The reduced fault some major repeater stations, to have outage time results from the use of the access to common records. These are used Network growth Service Protection Network. when setting-up make-good routes, and Over the period, we have seen the main identify private circuit customers affected by network grow from less than 150,000 circuits National NCC output network abnormalities so they can be to about 420,000 circuits. To accommodate NCCs, in addition to being involved in the day­ informed. In spite of these improvements we these there were about 330 coaxial and to-day operational control of the network, are, of course, still dependent on getting microwave radio links in 1968, whereas there produce regular reports on network accurate and timely information about are now some 1650. performance. National NCC produce regular network changes. statistics tailored to meet the needs of Equipment improvements various committees, and weekly summaries Failure reports At the start of our existence, all transmission of major service failures. The statistics have During 1983 the NNCC received over 4000 systems employed frequency division been used to indicate trends in performance reports of major service failures and multiplexing (FDM) and virtually all were valve and to estimate required network miscellaneous events. Of these, some 800 -+ 19 Cellular radio related to HF link failures which, in turn, contingency plans to cover catastrophic fault Telecom Securicor Cellular Radio Ltd contributed to the loss of 2200 hypergroups. situations, such as a complete failure of (TSCR), a subsidiary of British Telecom, 1000 reports were received from exchanges submarine cables to the Channel Islands. has recently been launched. Here is an which suffered restricted service or isolation. outline extracted from "The Review" of Failures to television links reported to the The future the market situation, together with an NNCC totalled 820, and 875 programme There are two major features that should be explanation of how cellular radio works. circuit failures were also notified. mentioned. One is the introduction of the Soon we will see the introduction to Britain Included in the total of reports received automatically switched digital SPN (ASDSPN) of a new telecom technology which should were about 800 relating to miscellaneous which will operate at the 120/140 Mbit/s level. boost BT's business. events which are not normally classified for This will be computer operated and will But much will depend on whether the race statistical purposes. include a telemetering system which will for customers is won by TSCR, the joint inform NCCs of route failures and the current British Telecom-Securicor cellular radio Planned Work authorisation {Form A60) configuration of the network. The system will company, rather than private sector rivals In the course of 1983, the planned work duty produce an historic record of operations and Racal Millicom. processed and authorised over 2400 planned this will be used for statistical analysis. Both groups have been given a licence to works. These included authorisation to cover The other feature is likely to bring together operate and will compete for the same remedial work on trunk cables to ensure that the NCC and network traffic management customers throughout the UK. Both have the performance of the coaxial pairs would functions under one roof in a Network been told by the Government to offer a be up to standard for digital transmission. The Management Centre. service to over 90 per cent of the country by protracted nature of this work placed an even (01-257 2241) the end of 1989. heavier burden on the Service Protection The fight will be fierce. TSCR (in which BT Network (SPN) facilities. owns a majority of the shares) will use British Also contained in the total 2400 planned Telecom engineers to plan, design, install, works were 400 jobs which required plant to commission and maintain the system of base be released from service for periods in stations, transmitters, receivers and excess of one minute, and hence switches. Much of the equipment will be necessitated the issue of a Form A60. In installed in BT premises. addition, the early part of this year also saw BT will also act as one of the system's the introduction of procedures to deal with retailers- selling and installing handsets and the digital network and in particular the billing its customers. 'X-stream' services. Large numbers of BT staff are already As well as this, the duty has a continuing active in a number of areas of work. commitment to produce and maintain As Racal and TSCR are competing for 20 Blinded II~ Public Network the light t exactly the same customers. the amount of by Dave Haskell BTWMITEM 3.2 1 extra work com1ng BTs way depends on who All too often the stable door is closed after is the more successful company. the horse has bolted I Sadly th1s has Cellular radio, the latest telecom frequently been the case in the provision of technology, is expected to create entirely effective voltage surge protection for External new business, and will not rival the BT Overhead and Underground Plant. network. Due to the sporadic and unpredictable It offers business people a new technology nature of electrical storms, the extent of which enables them to be in touch wherever damage that can occur from direct and they are. indirect lightning strikes tends to be How it works As well as handsets in cars, truly portable minimised in a lot of minds. In the past luck, Br1tain is divided up 1nto 'cells' varying 1n s1ze telephones will be available, for the first time. rather than good judgement, has saved the trom 2 miles across to some 30 m1les across The service will be a great improvement on day on numerous occasions. However, the according to local terrain and likely customer present car radio telephones. advent of voltage sensitive electronic numbers. The equipment for the network is being In each cell there will be a transmitter/ switching systems means that consideration supplied by Motorola, which, although an has to be given to effective protection­ receiver American company (the UK's cellular radio Customers travelling around Britain will otherwise the business will pay heavily in technology is based on an American system) simply dial the number they want on their terms of loss of service, damage, and does have a large base at Basingstoke, renewal costs. Above all there is the safety mobile handset. where, increasingly, equipment for the The handset sends out a signal that hits r1sk. which clearly cannot be overlooked. system will be manufactured. the nearest transmitter/receiver. Examine your own records and you will be BT's licence requires a coverage of 90 per This transmitter/receiver will change as the sure to find many instances where damage cent of the UK by the end of 1989. customer moves through different area has occurred to plant due to ineffective 'cells'. But the customer will be unaware of protection. If so, read on I any change. The transmitter/receivers connect with the Donner und Blitzen A typical cumulonimbus storm cloud- as BT network. Calls are logged on a central computer for shown in figure 1 -is created by a rapid accounting purposes. upsurge of warm, moist, air to great heights. Strong air movements take place with winds reaching altitudes of 10,000 metres, With acknowledgements to The Review/April and cooling of the elevated air masses leads 1984. to heavy condensation. The storm clouds - 21 Ftgure 1: Formation of a typical cumulonimbus storm cloud reach heights at which temperatures are nearby ground strike can induce very high Altitude below 0 degrees Celsius, resulting in voltages, resulting in considerable damage kM precipitation in the form of ice crystals or not only to nearby plant but, because of the super-cooled droplets. Usually both forms are conductivity of our cable network, also over a 10 + present and the alternation between ice and very large area. + + water droplets produces a high electrical potential. The negative and positive charges Gas discharge tubes 9 ~ /I are separated owing to the different speeds The devices in use for protection of the ~I \I t I I I at which ice and water fall, so the clouds act External Plant Network are commonly known \ I I I . / 8 I I as generators. When the air becomes as Gas Discharge Tubes and the Vocabulary overcharged, a lightning discharge is of Engineering Stores defines them as \ ~ I 'I , produced. The resulting sudden increase in Protectors. A gas discharge tube consists of 7 pressure in the path heated by the lightning, two electrodes in a small evacuated envelope \ I leads to a shock wave heard as thunder. into which a small quantity of rare gas has 6 The electrical potential of a strike can been introduced. It 'fires' at about 210 volts reach 100 million volts and the current can and has a switching time in the order of 5 be up to 200,000 amperes, although an microseconds. At the striking voltage a t average value is nearer to 25,000 amps. discharge is established and the device ~\ The energy Involved in each lightning flash conducts. When this voltage disappears the 4 t I ~ \ \ is about 100 kilowatt hours, enough to supply gas discharge tube ceases conducting and I I ~ \ the average household with electricity for a restores to normal. 3 I ;· \ \ week or more. Devices in use at present are mainly \ \ Fortunately, the number of actual strikes is protectors 5A, 14A, 17 A and 18A 2 I very small small in proportion to the total Protectors 5A are used to provide number of lightning flashes, since many protection at primary connection points occur as discharges from cloud to cloud. If a (PCP's), customers' premises and at Radio fire is caused it is usually the result of and TV Stat1ons. It is a plug-in device and one ~ J ~ warm lightning with a long discharge duration. Very is required for each leg of the pair. Protectors I I , brief flashes are termed cold strikes since­ 14A are three-pin plug-in devices, the centre I ,·' I I although temperatures of 10,000 degrees pin being the earth connection and the outer I ;/; em:~,., Celsius are reached- they are too short-lived pins line connections. Their main function is I ~\\ to ignite the material involved. to provide protection on main distribution Because of the high voltages involved in a frames (MDF's). + + Ground + + lightning strike, it does not require a direct Protectors 17 A and 18A are basically an + + strike to harm telecommunications plant. A encapsulated Protector 14A with three 22 External line plant protection Pole terminating wires. The two short red wires points along the route. Obviously, the number Preferred method are the line connections and the long green of additional protection points will depend on Aerial wire is the earth connection. This device is the length of the route and the probability of cable- Protection predominantly used for providing protection lightning on the length of the route and the joint in underground and aerial cable joints. probability of lightning strikes. See figure 3. Network Only one Protector 14A, 17 A or 18A is Should the aerial cable route contain a Earth cable 1 joint used per pair of wires. number of High Grade circuits- and loss of Joint box 1 service cannot be tolerated- it is suggested Lightning protection joints that gas discharge tube protection is BTWM have pursued the development of the provided at the ends of the exposed section, cap-ended Sleeve 31A and 32A as a lightning and a steel catenary wire suspended about 4 protection joint using protectors of the 17 A inches above the aerial cable for the length type. Figure 2 details their recommended of the route. The catenary wire will be use. Sleeves 31A and 32A can provide bonded to the earth at the protection points protection for up to 50 and 100 pairs and earthed at, say, every 4 or 5 poles along respectively. the route. To ensure that a good quality joint is The catenary wire will then act as a Alternative method achieved, BTWM supply a kit containing all lightning conductor Pole---­ the necessary items to produce a protected Aerial cable joint. They are known as 'kits closure TV and radio station protection lightning protection 17 A', (KCLP17 A). At radio stations the requirement is to Currently, over 5000 kits have been supplied safeguard BT plant, personnel and customers to the field without any reports of fa1lure so both within and outside the rise-of-earth­ far- in fact, the feedback has been very potentia! area. This 1s currently being encouraging. achieved by employing the 'equalisation method' rather than the 'isolation method' of Aerial cable and dropwire protection protection, see figure 4. In the External Plant Network the aim is to Radio stations, by their nature, are protect BT plant, personnel and customers at extremely prone to electrical discharges extremes of the network. The exposed from the atmosphere- much more so than overhead cable can be sacrificed, so long as external plant overhead cables, so have to be Figure 2 (b) the 'E' and 'D'-sides of the network are treated accordingly. protected. Damage can be minimised on long If protection at radio stations is not carried aerial cable routes by 'fragmentation'- that out correctly, situations hazardous to BT is, by providing protection at intermediate plant, personnel and customers can arise. It+ 23 Figure 3: AIC = aerial cable Example of aerial cable and dropwire lightning protection. PIW = drop wire

PU = point at which protection should be applied

DP AIC AIC A!C AIC AIC AIC AIC AIC AIC AIC

PU PU PU Underground cable to exchange

Figure 4: ~~i... '+_io_n_at-[_T_V_a_nd-ra_d_~:_:_~~-~_::_:_:_e_t-ho-d------i~-=rn is imperative then, that the correct principle is employed coupled with a high standard of Isolation transtormer workmanship. With the 'equalisation method', protectors Exchange Station I Line I are provided at the station and at a point along the station feeder cable defined as the Equalisation method 'second protection point'. When lightning I strikes, the potential of the ground around the ----..___ ~ mast rises by several thousand volts Gas discharge tubes 1 compared to the ground potential at the ... ------~ distant exchange. This voltage places extreme stresses on BT equipment and the Second cable feeding the site. To overcome this, protection Case 219A protectors are connected to every cable point conductor. At the instant of a lightning strike 24 Letter the protectors allow the station ground copper tape, earth spikes and rods. potential to appear on the cable conductors It must be pointed out. though, that the in an attempt to equalise the potential. only meaningful evaluation of an earth Our Merlin correspondent, who informed us This is where the 'second protection point' electrode is by means of an electrical test. so about corrosion of line jack units in MN24, is vitally important- not only in correct this procedure is recommended in all cases. draws our attention to something new .. positioning away from the mast. but also in the quality of the workmanship- since it is at Future trends Trunking for Box Connections 300 this point that the surge on the cable has to In an effort to contain costs and improve on For several years the installation of a Box be 'dumped' If the 'second protection point' productivity a new kit (kits closure lightning Connection 300 meant the installation of is incorrectly situated, or suffers from inferior protection 18A) is being developed. The several feet of visible and unsightly cable. workmanship, the surge will pass along the matrix board of the new kit will- for the same , A new trunking system has just been cable into main cable network with disastrous overall dimensions- have double the introduced for use with the Box Connection and possibly fatal results I capacity as that of the KCLP17 A Also. the and Merlin system boxes. new matrix board will have an in-built It comprises of the following three Provision of earth electrodes earthing strip, thereby reducing the parts components: The provision of a good Earth cannot be over contained in the kit and make for easier and emphasised. It is a waste of money providing quicker connection of the protectors. Item protective devices only to provide an Finally. good lightning protection not only Item Code use ineffective Earth. safeguards plant and personnel- it is also Cable 07 227 4 Replaces an end Where lightning protection devices have cost effective. With kits now under £10 the funnel 1A panel in a Box been fitted and shown to be inefficient. it is cost is recovered the first time a fault is Connection 300 and nearly always because little or no attention prevented. provides a neat has been given to the provision of a good As the title of this article suggests. don't be interface to the Earth. Blinded by the Light. but open your eyes to Trunking 4A It should be noted that the value of the the savings possible- in lives and cash- by Earth required for external plant overhead good protection. Trunking 4A 07 2272 2inch x 4inch plastic cables is 40 ohms or less. and 20 ohms or (0222 391433) trunking with clip-on less for the 'second protection point' at radio lid supplied in 2m stations. lengths It is for this reason that the latest Elbow 1A 07 2273 Elbow 1A 90 degree instructions on the lightning protection of plast1c elbow for use external overhead plant and radio stations. with Trunking 4A now have a table of requirements to produce an Earth of the above resistance values in soils of different volume resistivities. using 25 National Networks: trunll serviees-naaintenanee

by Peter McKenzie NN/TS02.3.6 upon it as a Business, At the end of June 1984 National Networks • to take and implement decisions faster, it Trunk Services employed nearly 9350 staff, was realised that smaller, more 61 per cent of them in the largest Division: manageable, units were needed, based on cable TS02- the Maintenance division. But what is the new market segments. funnel 1A the role of this Division and what is the size of the Network maintained by them? Before The Structure answering these questions perhaps we To meet its responsibilities, NN has been set should ask, why National Networks? up as two separate profit centres- Trunk Services (TS) and Specialised Services (SS). to system The reasons TS has business responsibility for the STD National Networks (NN) was created in the services, SS has responsibility for a wide Spring of 1982. The BT Board's reasons for range of services including Telex, Packet splitting the then Inland Division into NN and Switching and long distance private circuits. Local Communications Services (LCS), as independent profit accountable businesses, The size elbow trunking 1A joint made on site by fitter were based on two driving forces, one TS Division became fully operational in April external and one internal. 1983 at District Office level. During the o The external forces included- following year District Office staff, and • the emerging competition- the licensing of District Managers Trunk Service (DMTSs), The system boxes for Merlin's Regent (Box Mercury being only the tip of the iceberg planned and managed the orderly transfer of Connection 350) and Herald S51 02 (Box • customers' expectations- as customers some 7600 Area staff into the TS Divisions. Connection 335 and 336) are being issued become more reliant on telecommuni­ As at the end of June 1984 the distribution with Cable Funnels 1A already attached, cations they place increasing demands on of staff was as follows: enabling direct connection to the trunking. their telecommunications suppliers to So the next time you visit a site why not improve, and add to, the services provided neaten it up with a bit of trunking? • technology- technology now provides the R Coates, BT Merlin/SE 2.1.3, (0394 693467). capacity to deliver the new services customers require. o The internal forces included- • the fact that to meet the external forces, if run in the old traditional monolithic form, BT could not meet the demands being made 26 to and including GSCs or Digital Main maintenance of all analogue and digital line Trunk Services Division Reference Staff Nos Switching Units (DMSUs) and radio equipment, together with The trunk network currently consists of associated cables, used for both trunk and Operations TS01 650 more than 417,000 trunk circuits controlled special services in the trunk network. Maintenance TS02 5-r38 from 435 Trunk Maintenance Control Centres In the switching field it covers the (TMCCs) There are 444 group, transit and maintenance of all space and time-division Systems Engineering TSP1 132 sector switching units, served by well over equipment and systems used for switching of Transmission & 600 repeater stations and 195 radio stations. trunk traffic, including access to international Switching Planning TSP2 284 These represent an asset base with a value routes. Transmission Works TSP3 1106 Switching Works TSP4 1176 exceeding £14 billion. It is also a network From Head Office to District level the which is growing and absorbing new policy is one of involvement, and the work of Finance TSF 83 technology. While the existing analogue the Division can be broadly summarised as: Commercial TSCM 19 network will continue to function until the late • pre service work- assisting designers and 1980s, a digital network will grow alongside. planners at specification stage about the Personnel TSPM 80 More digital transmission systems are maintenance facilities and documentation already in service and the initial Digital Main required for new services and equipment, Computing Strategy TSCS 79 Switching Units (DMSUs) are coming into • acceptance into service- liaison with service. Eventually there will be 60 large, fully installation staff to ensure the supply of TOTAL 9347 interconnected, DMSUs capable of providing facilities necessary for the efficient enhanced STD services and allowing the operation and maintenance of new With a relatively small staff- 3.9 per cent introduction of new competitive services. systems, test equipment and spares, of BT's total workforce- Trunk Services is Good marketing and selling alone does not • operation, maintenance and technical organised vertically; that is, all Planning and sell new services unless they themselves are support- recommending methods of Works is integrated into one structure from effective and backed up by an efficient operation and maintenance to achieve, Head Office to District level- and similarly maintenance team. This maintenance team efficiently, the required standards and for Operations and Maintenance. The also includes LCS staff. establishing procedures to monitor results. purpose of this is to create an organisation Organising repair arrangements and more responsive to take on the major The Maintenance Division providing technical support as required, technical and commercial tasks of the next The vast majority of the Regional and Area • second line development- developing few years- particularly that of changing the staff transferred to N NfTS are now in the solutions to problems encountered in trunk network from analogue to digital Maintenance Division (TS02). service. technology. The vertical structure also The overall responsibility of TS02 is to ensures that lines of communication are determine and implement such policy as is The role of the DMTS short and information can pass rapidly necessary to ensure the economic Within TS02, the day-to-day maintenance of through the Division. maintenance- and progressive improvement TS plant throughout the country is managed In terms of assets NN owns trunk -of the standard of service, provided by the by the DMTSs whose current geographic transmission down to Group Switching transmission and switching plant in the trunk responsibilities are roughly in line with the Centres (GSCs) or Digital Principal Local network. previous Regional boundaries. Exchanges (DPLEs) and trunk switching down In the transmission field this includes the DMTSs report direct to the Chief Engineer, -+27 Figure 1: The position of the DMTS in the NNITS organisation

District District District Provincial District District District Finance Operational Maintenance - Districts ----.. Planning Transmission Switching Staff Staff Staff Staff Works Works Staff Staff London only 0 & M Organisation Key:- Full executive SDLM Senior Divisional Line Manager responsibilities DMTS Is the SDLM for TSO 1 and TSO 2- National oversight and Provinces, and TSO 2 only in London responsibility for DPM District Personnel Manager policy and standards TSCS Trunk Services Computer Strategy - _J L __ _ District day to day CETS Chief Executive Trunk Services I SDLM I control and co­ ordination District District Operational Maintenance District co-ordination Staff Staff only

Operations and Maintenance and, in addition Agency working General Managers. to their in-line responsibilities for While the aim of the new organisation is to be The reasons for this include- Maintenance and Operations, they also have as independent as possible, there will be a • physical- ducts carrying both NN & LCS indirect responsibility for Planning, Works, need to continue to use LCS staff for cable, and GSCs with subscribers, Finance and Personnel staff in Districts maintenance work in the early years. • economic- small elements of NN work that whose in-line managers are located in Head For some things it will be more practicable would not justify the establishment of an Office. to pay others to do work for NNfTS. This NN work force, Figure 1 illustrates the TS organisation and 'agency work' will be covered by Agency • social- staff remote from the main centres the position of the DMTS. Agreements between the DMTSs and of NN activity who would not feel part of the 28 Eleetronie eonaponent Fast Response Serviee- FRS

new organisation, by Andrew Pagan, shows the FRS flow process. • variable work loads- patterns of work that Materials Department M6324 Comprehensive Technical support­ peak for short periods only. 1 Issue 2 of the FRS catalogue was including reliability data, ESD advice, item There will be, of course, instances where published in July and contained approval and assessment of equivalents- is TS02 will act as agents for others, for approximately 1300 items for general available through FRS links with the Materials example when TS02 staff maintain the local maintenance, repair, and planning, as well and Component Centre (MCC) in Birmingham element of a non-dedicated GSC, or do as for 11 specific product ranges. Further and London (see following article). maintenance work for BTl or, indeed, for items have since been introduced for Coin The FRS catalogue and price list gives NN/SS on an agency basis. Telephone 228 and Senator. details of all product ranges stocked. If you The policy of same-day despatch is have problems obtaining components please Corporate concern working well and field staff are Increasingly contact us- we may be able to source the 1 Looking forward in the new competitive using the telephone ordering facility which item for you environment which now faces us, it is evident gives immediate access to stock availability Catalogu es and further details of the that effective maintenance activity has a and requires no follow-up paperwork. Telex, system can be obtained from Andrew Pagan major role to play in NN/TSs future. The facsimile and post for A 1063 details are on 0793 48 4572. quality of this maintenance activity is alternative methods of ordering. The figure paramount, particularly at a time when our customers' perception of quality of service FRS flow process 8.30am- 4.00pm leaves room for improvement. Overall quality telephone of service is a Corporate concern and it is Repair Bridgwater only through maintenance staff in N N & telex Maintenance FRS Private depot LCS- working as a team- that the quality of fax r- Planning Swindon Wire FRS maintenance activity, and hence service, will staff A 1063(post) link improve. (01-432 9310) A10~3S

Area Same day despatch accounts/clerical by first class post Groups to all parts of BT

-29 Pat Keates and Michael Bleadon of Swindon 's Fast Response Service seen processmg orders for electronic components. 30 The Materials and Stop press Conaponents Centre (MCC) by Trevor Morton-Holmes MC2.3 • Testing, evaluation, analysis and advice on Avoid cheap plugs MCC provides the following support the use of materials An article in a recent issue of 'Safety Scene' functions- • Custody and maintenance of BT referred to the potential hazards of using 13 • Advice on selection, availability and mechanical standards, dimensional Amp plugs from non-approved sources. The reliability of all materials and electronic metrology, dynamic testing, proof-testing essence of that article is included here. components and non-destructive testing The 13 Amp plug is common enough • Component identification, sourcing and • Electrical safety test1ng of apparatus. nowadays and we are probably all guilty of replacements for obsolete components Remember, you can talk to us directly nipping into the local shop to buy one so that • Advice on prevention of Electro-Static about any task or difficulty you are a new piece of equipment can be tned out. Discharge (ESD) and trouble shooting experiencing and we will try to help you What we may not appreciate, is that many • Component, equipment and system Our motto is 'Help us to help you keep BT plugs purchased from bulk suppliers can be reliability data collection and analysis ahead'. of indeterminate and variable specification • Testing, evaluation, failure analysis and For further information please contact with- it seems- little regard for electrical reliability assessment of components and John Mottram on 021-772 2361 Extn 2529. safety. assemblies It is easy to catch out the unwary, too, because people believe they are buying a safe product when it is clearly embossed BS1363- the appropriate British Standard Specification for 13 Amp plugs. Unfortunately, this number gives no guarantee of actual compliance. Purchasers should be particularly wary of plugs which have a 'V' -shaped fuse holder, and those which do not have separate compartments to prevent detached wires from touch1ng other i terminals. The simple message is: obtain your plugs from BT stores whenever possible. If you do buy locally, select yours from a reputable manufacturer. Any enquiries to Peter Brunton, LLS5.1.2, 01-739 3464 Ext 421.

31 If you have a contribution to offer to Maintenance News other than a letter to the editor, please forward it to your Maintenance News agent listed below. The Editor cannot publish anything to do with current awards suggestions, neither can he be held responsible for technical inaccuracies in authors' submitted text. Send ~our eontributions to • • • BT EAST Mr P F Johnson LM1.2.1 0206 89588 BT INTERNATIONAL Mr D A Bardouleau IL3.3.3.3 01-936 3368 BT LONDON Mr E Jones S11 01-587 8000x7 489 BT MIDLAND Mr C R Webbley PG2 021-466 529 BT NORTH EAST Mr R Mundy MCS1.2.1.1 0532 466 529 BT NORTHERN IRELAND Mr J McLarnon ME5 0232 231594 BT NORTH WEST Mr R Walker S2.2 061-863 7 459 BT SCOTLAND Mr P McElroy S1 1.5/1 031-222 2390 BT SOUTH EAST Mr R E Weddell LN/LE 2 0273201517 BT SOUTH WEST Mr J 0 West TS02 0272 295337 BT WALES & MARCHES Mr T G Baker CCD2.1.1 0222 391223 NATIONAL NETWORKS Mr P McKenzie TS02.3.6 01-432 9310 32