Maintenance News 20 Spring-Summer 1982
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Contents Ed1tor: Ron Quinney (ES5.4.3) Editorial Publ1shed by BTHO/ NE / ES543. Testing SSAC15 Pr1vate C1rcu1ts Room 301. at TMCCS 203 High Holborn Improvement plan for overhead LONDON WC1 V 7BU network 3 01 -432 2806 Special serv1ces maintenance 4 Maintenance News D1g1tal transmiSSion- coded mark ISSN 0143-6627 1nversion 5 How computers keep their cool 6 Regent call connect system 7 The Irish connection 10 Register translator 14 11 Close encounters of the 4A kind 14 On reflection. 15 New generation test equipment for the fault repair serv1ce 17 Faster RATES for private circuitS 20 Automatic testmg methods 21 New cable alarm saves money 24 New electroniC work bench 25 Introducing reg1onal service 1mprovement centres 26 Letters 26 Editorial Testing SSACIS private eireuits at TMCCs My editorral functrons on thrs magazine take by Roy Smith BTM/SM1.4 Operation up only a small part of my BTHO duties. The success of the patching relay set In operatror1. orther the local or drstar1t~end lnevrtably. therefore. time does not permrt used with the signalling system AC13 of the crrcurt to be tested rs patched from the complete checkrng of the technical accuracy (SSAC13) at Trunk Maintenance test Jack frame ( T J F) appear a 11 ce to the test of all authors' submrtted drafts. This was Control Centres (TMCCs) resulted in set. due regard bern~l grverl to the TMCC brought home after the drstrrbution of the decision to introduce a similar standard levels. The patch should. therefore. MN19 by my training colleagues who were device for circuits equipped with the rncl ude ar1y r1ecessary a mplrfrers and becomrng bombarded wrth querres on AC15 equipment. The facilities offered attenuators. The AC15 rs r10rmally strapped Herald trainrng courses- all because two by the tester and some constructional to present relatrve levels of 1 dBm and course numbers had been transposed. The details are described in this article. It -4d Bm. Having done thrs. testrng can start. Edrtorral Board have 11ow decrded that a should be noted that this BT version ..J Outgoing call disclaimer should be rncluded in the has identical electrical characteristics The two~wrre lrne test cord rs plugged into magazine in future. In my other dutres. to the Northern Telecom equipment. the two~wrre Jack and, after operating the concerned with the reparr of electronic Facilities 'speak' and 'loop hold' keys, the required equipment. I am aware of the wrde variety of outgomg call-rr1cludrr1g dralling to local number is dialled. Wrth restoratron of the new customer apparatus. systems and e or drstant~er1d 'dral' key, supervrsory tones are heard. When technology enterrng servrce with British rncomrrlg call-rr1cludrng recording of the drstant~end answers. the lamp lrghts Telecom- many in large numbers. The e dralled drgrts on a 10 or 16~digit drs play rndrcatrng Called Subscrrber Answer (CSA) exciting and challenging era we have been unrt -and corwersation can take place. waiting for has arrived. and it rs up to all of us supervrsory condrtions When the called~er1d clears (CSA lamp to keep ourselves informed of developments. e -rncoming call (1/C Call) off) the crrcurt can be released by restoring Maintenance News arms to do all it can to -called subscrrberanswer (CSA) the 'loop hold' key. help in this important aspect of today's ~-called subscrrber clear world.- Edrtor. J Incoming call e M onrtor of cr rcu rt- tone on idle The customer or engrneer at the drstant~end Equipment can then be rnstructed to call back. In thrs As shown in the crrcuit diagram. the rnarn case the lamp mdrcates an rncoming call features are: (1/C Call). The procedure already e interface relay set -loop drscor1nect/E mentruned rs followed. but thrs trrne the and M rr1comrng dralled drgrts can be detected and e transformer unrt stored 011 the drsplay unit. e break~type Jacks and lamp The crrcurtrs released wher1 the callrng~ e SSAC1 5 equrpment end clears. Benefits • elimination of abortive visits to customers Several benefits arise using this test-set, e improved serviceability. including: 021-262 4040 e fault localisation before involving other maintenance staff Edge connector T1 .-------------~5 +6 4 R4 s British Telecom LS SSACIS 2 Equipment Diag SA/SAW 702060 -50v 0 35 II~ LS2 1 111 _-/ ... riD lJI,1 -ve .., E2 .., ~S:,1 I 212~1 Digit e---'-"-------------------- ~ I ~II 1 Display Reset 21 22 1 2 I A::: r<:/\ _/(2 Unit ~~~----------------------~ 11H1vvv~ E---111 1/C Caii/CSA lamp Improvement plan for overhead netUJork by John Stoddart BTSW/SV1.3.2 wrre. such actron often manifests rtself as an when they encounter or provide more than New developments over the past 10 rntermittent norse fault. Wmk practices two drop wires in line of route years have steadily improved the considered to contrrbute to premature drop e too low a priority given to dealing with any performance of the overhead network. wire failures are: ofthese causes. But this performance tends to e too many drop-wrre clamps frxed to a deteriorate rapidly during bad weather. srngle Bracket 22 often result rn abrasron Improvements required This inability to withstand bad weather e strippmg rrlsulation unnecessanly or failing . j More reliable drop wire not only stretches the manpower to use the cmrect tool- Wire Stnpper 2- BTHO seem to have accepted this and a drop resources beyond the limits of the results in damage to the conductor wtre wtth cadmtum-copper conductors, to be normal repair service organisation, but e JOtntt ng drop w1 res wtth Wire Insulated known as Drop Wtre 7, is to be introduced also has a catastrophic effect on BT's Connector 1 A- which is for underground natronally. ability to restore customer service use rapidly enough to achieve the TIP 2 e failure to use an Aerial 32A and Tester 132 _j Improved workmanship target. Consequently, as BT is soon to to locate a disconnection fault can result in Even wrth the Introduction of a more rei table aim for a 95 per cent TIP 2 target and the creation of unnecessary JOints. drop wtre. staff need to become aware of also has a longer term Tl P 1 objective Srmilarly, unwillingness to open aerial preventive matntenance aspects, such as: of 0·29 fault reports per station per cable couplings results in additional joints e The prevention of drop wtre fat lures which annum, further effort must be directed external to the couplings are a result of abrastorl by trees, lamp towards reducing the overhead plant • insufficienttree pruning. standards. roofs and so on fault rate. Other causes are: e J ornts 111 drop wtre must be kept to a elack of a suitable lead-in cable at block mirlrmum and, whenever practical. a faulty Factors affecting performance wiring points drop wire should be replaced in its entirety. Wrth the exceptron of Drop Wrre 4, other • ageing of open wires and the inability of Where Joints are unavoidable, the correct recent types have been rnadequate. The staff to carry out their work rtem- Wire Connector 2A- must be used situatron rs further aggravated when there rs • insufficient use of spiral eyes to restrict the e Staff should carry S!Jare terminal block an accumulatio11 of drop wrres on a route. movement of drop wires to reduce covers and strip-contact gas-discharge Frequer1t failures occur because drop wires termination failures on DPs tubes which should be replaced when they are unable to withstand abrasron and are thus • the conductors of both an aerial cable and are found to be corroded susceptible to any fmm of abuse arrsing drop wires terminated on the face of a e Terminal blocks should be treated with from pom corlstructrorl or work practices. terminal block often results in the drop srlrcon spray as a matter of course Resultir1g damage to the copper-coated steel wires being severed by the aerial cable • Frnally, good field supervision and conductor soon causes rt to cmrode or rust • failure of maintenance and installation staff adequate trainrng are essential ingredrents away. Before the complete far lure of the drop to subm rt either forms A 1 024 or A2887 to improve the quality of workmanship. 3 Speeial serviees naaintenanee J Comprehensive plant improvement by Don Beckley T5 much more cooperation and extra effort w1ll scheme Private circuits are the most important be needed. There is a need to introduce an all-embracing part of Special Services, of which Even before the threat of competition it scheme which will- amplified external extensions and Datel was recogn1sed that BT may not be showing • include procedures to identify sections of services are the other large elements. enough concern. but with competition now overhead plant which are in need of Because of their importance private with us we have greater reasons for remedial attention circuits have been under the spot-light satisfying our pr1vate circuit customers. In e be complementary to LOCAMS recently due to the long delays in the Bell system, one-third of the revenue • have a mechanism to control the priority of provision. Consequently there has not comes from spec1al services. compared with the planning and execution of plant been much attention focused on four per cent in the UK. wh1ch illustrates the improvement work. maintenance. This is not to say that all considerable potent1al for shift of revenue by To conclude. adequate numbers of the our customers are satisfied with their our business customers. correct size working parties will be required service, indeed, the need to improve the to support such a plant improvement repair service still exists- especially in TIP2A programme.