152 Train Telephone Communication System employed by the By W. R. Triem General Superintendent of Telegraph, Pennsylvania provides Pennsylvania Railroad, Philadelphia, Pa. continuous communica· tion between trains, be· tween front and rear of trains, and between trains and wayside towers A LONG felt need for a means of com­ munication between trains, whether moving or standing, and between trains and wayside stations is be­ lieved to have been met in the train telephone system being given trials on the Belvidere branch of the New York Division of the Pennsylvania Railroad. This telephone system is the result of joint development by the Pennsylvania and other rail­ roads* with the Union Switch & Sig­ nal Company over a period of sev­ eral years. Since the earliest clays of experimentation with radio, the rail­ Engineman using the train telephone to talk with a block operator miles away roads and manufacturers of electri­ cal equipment have been attempting to solve the problem of providing of axles for cracks, Sperry. apparatus far as radio is concerned, it must be reliable communication on and be­ for detecting flaws in rails, and the remembered that, essentially, com­ tween railroad trains and wayside like. munications by radio are broadcast stations. to all suitably tuned receiving sets This innovation is the latest of a Cab Signaling Leads to Communi­ within transmission cl i s t a n c e s long list of improvements developed cation System through ground and atmosphere; by the Pennsylvania and other rail­ i.e., through transmission paths uni­ roads in co-operation with various Among these, an outstanding con­ versally provided by nature. Radio electrical manufacturers to expedite tribution to train operation is the cab would possibly fulfill the require­ train movements and afford better signal, by means of which a signal is ments of communication between service for the public. Discoveries displayed in the cab of an engine moving trains and between moving and developments in the field of elec­ reproducing wayside signal indica­ trains and wayside stations if it were tronics have been utilized by the tions and keeping the engineman not necessary to share with others railroads in numerous ways, and constantly advised of the conditions the privilege of the air and conform constant research is under way to on the track ahead of his train. In to Federal rules and regulations so find means of further increasing the the development of this cab signal essential to the maintenance of order efficiency of railroad operations. system, it was found that a further under crowded and competitive con­ Among more recent contributions in extension of the application of elec­ ditions. On the other hand, wire the field of electrical and electronic tronics to railroad operation was telephony does not fulfill all of the developments are centralized traffic possible to provide a means of com­ requirements of communication be­ control, dragging equipment detec­ munication between moving trains, tween moving· trains and wayside tors, cab signals, radio-telephone and between moving trains and way­ stations for the reason it is confined tugboat dispatching, telephone an­ side stations. to definite wire transmission paths nouncing systems in yards and sta­ The train telephone in use on the from the transmitter to the receiver. tions, yard engine telephone systems, Pennsylvania Railroad today, is a The train telephone system in use magnaflux method of examination result of these studies. Actually, it by the P ennsylvania on the Belvi­ is neither radio nor telephone. It dere branch combines certain fea­ *Editor's Note-For detailed explanation of cir· incorporates certain features of both tures of radio and wire telephony, cuits and apparatus, see page 665 of Railway Signaling for December, 1943. For explanation types of equipment and eliminates utilizing the constant contact with of installation of this communication system -on Bessemer & Lake Erie, see page 387 of July, 19 40 . other features of both systems. So moving vehicles possible by radio March, 1944 RAILWAY SIGNALING 153 and at the same time restricting the transmission paths to railroad prop­ erty. Railroad vehicles invariably The block operator use track rails which extend to all uses t r a in tele­ phone to call the areas requiring communication with crew of a freight moving equipment. Thus the rails train miles away offer a most desirable communica­ tion transmission path. The rails, control box; necessary wiring and A freight train conduit. conductor calls The equipment box or instrument his engine c r e w shelter on the engine is located on on the telephone the running board near the front end, the output transformer is in front of and below the smokebox, together with adjacent communica­ truck to adjacent track via the rails, the receiving coils are about 4 in. tion pole lines, are utilized for the and a current at carrier frequency is above top of each rail and located transmisison paths and the electronic sent out along the rails and adjacent between the engine truck and front equipment, electron tubes, condens­ line wires with . the return path drivers, the loud-speaker is in roof ers, coils, and the like, on engines, through the ground. The impedance of cab above engineman, the control cabin cars and wayside sta{ions pro­ drop in the rails between the insu­ box with calling button, indication vide the means of utilizing radio lated truck and adjacent truck causes lamps, volume control and handset is principfes in maintaining the con­ the transmitting rail voltage. Re­ in cab above and in front of engine­ stant communication contact so es­ ceivers pick up the energy which is man. sential to the success of the scheme. transmitted through induction coils The equipment box and storage in proximity of the rails and is am­ battery in the cabin car are under Tests Started in 1941 plified and demodulated for recep­ one of the seats; the output trans­ tion in the loud speakers and hand­ former is under the cabin car about Experimental installation of the set telephones. midway between the trucks ; the re­ Union Train Communication System A the station, the output or trans­ ceiving coils are about 4 in. above on the Belvidere branch was author­ mitting connections from the set, top of each rail between the trucks; ized in September, 1941, and in June, when talking or signaling, are made loud-speaker is in the cupola; con­ 1942, an engine and cabin car had to a simplex leg of a block line and trol box with calling button, indica­ been equipped, wayside appliances to the rail system, the circuit being tion lamps, volume control and hand­ installed and placed in service. To completed by the capacity coupling set are on a partition of the car. The date, 10 engines, 10 cabin cars and 1 between the block line and the rails removable equipment trays in the block station have been equipped, the length of the branch. The re­ equipment boxes on the engine and and an additional block station will ceiving connections at the station are cabin car are interchangeable. The soon be in service. made to the track rails at points electron tubes are the same as those It is a carrier telephone system about 150 ft. apart, the impedance used for telephone, radio and other using the upper side band of a 5,700- drop of which provides the energy purposes. cycle carrier for transmitting calling which is amplified and demodulated signals and voice. The carrier cur­ for reception. There is no interfer­ Block Station Equipment rent is fed conductively into the rails, ence in operation between this sys­ picked up inductively from the rails tem and radio, telephone or signal­ The block station equipment con­ and induced in the wires of the com­ ing systems. sists of a metal cabinet which houses munication line adjacent to the track. the electron tubes, coils, condensers, It is carried through the rails and Train Equipment rectifier, transformers, etc., for call­ line wires between front and rear ing, transmission and reception; a ends of trains, from one train to an­ The engine and cabin car equip­ desk stand microphone, with calling other train and to wayside stations ment consists of a weather-proof button and lamp indicator in the by direct-wire connections in the instrument shelter containing elec­ base and a head band receiver; foot vicinity of the station. tron tubes, condensers, coils, dyna­ switch for transmission; loud-speak­ At the sending telephone on the motor, fuses, etc.; a source of power er with volume control for reception engine and cabin car, a circuit is pro­ supply; an output transformer; two of calling signals and conversation. vided by a loop from an insulated receiving coils; a loudspeaker; a When head band receiver is being 154 RAILWAY SIGNALiNG March, 1944 Frenchtown. The telephone equip­ ment on engines and cabin cars is kept turned on continuously between these two points. vVhen the tele­ phone is to be used, a calling signa\ is first sent out by means of a push button on the control panel which causes an audible signal to sound in loud-speakers of receiving sets at the wayside station and on engines and cabin cars within the radius oi operation. The person calling. the 11 The bar of metal broadcasts the name of the station or shown below the the number of the engine of the t·rain cylinder is an end of receiving coil and whether engine or cabin car is being called, until response i ~ re­ ceived and telephone communication established. Benefits of the System Experience with the daily use oi the system on the Belvidere branch has shown numerous advantages, in movements of trains, by reason of the close contact which is constant­ ! v available between the train em- 6Joyees on the front and rear of trains and between them and the used, the loud-speaker is cut out.