Trainphone was the

Pennsylvania Railroad The Pennsylvania Railroad (reporting mark PRR), legal name The Pennsylvania Railroad Company also known as the "Pennsy", was an American Class I railroad that was established in 1846 and headquartered in Philadelphia, Pennsylvania. It was named ...

's system for voice communication between crews on moving trains, dispatchers, and tower operators. It was also used by the Kansas City Southern, and to a lesser extent on the Duluth, Missabe & Iron Range. It did not use radio, but rather

electromagnetic induction Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field. Michael Faraday is generally credited with the discovery of induction in 1831, and James Clerk ...

. Railroads did not own any

radio frequencies Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upper ...

at the time, and the PRR's busy network found the previous methods (passing a physical paper message, or requiring a train to stop to pick up orders) insufficient. The trainphone system was first tested in 1936 and perfected by 1943.

Equipment

Shore transmitter

The system used the

track Track or Tracks may refer to: Routes or imprints * Ancient trackway, any track or trail whose origin is lost in antiquity * Animal track, imprints left on surfaces that an animal walks across * Desire path, a line worn by people taking the shorte ...

itself, or lineside

telegraph Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas p ...

wires, as the "shore" transmitter. The trainphone signal — low frequency current in the hundreds of kilohertz — was passed through the track or wires and induced a corresponding current in the locomotive or car's receiving antenna. The range was only a hundred feet or so, but this was sufficient.

Antenna

Mobile trainphone antennas took the form of long, handrail-looking structures atop the tender of

steam locomotive A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, oil or, rarely, wood) to heat water in the locomot ...

s, atop the bodies of

diesel locomotive A diesel locomotive is a type of railway locomotive in which the prime mover is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is conveyed to the driving whee ...

s, or running the entire length of a

cabin car A caboose is a crewed North American railroad car coupled at the end of a freight train. Cabooses provide shelter for crew at the end of a train, who were formerly required in switching and shunting, keeping a lookout for load shifting, dama ...

(PRR term for

caboose A caboose is a crewed North American railroad car coupled at the end of a freight train. Cabooses provide shelter for crew at the end of a train, who were formerly required in switching and shunting, keeping a lookout for load shifting, damag ...

Telephone handset

The engineer or other crew member would talk through a regular-looking telephone handset. An attention loudspeaker was also installed, but it was easier to hear the messages with the handset.

Problems

The biggest problem with the trainphone system was that it could not work in

electrified Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. The broad meaning of the term, such as in the history of technology, economic history ...

zones, because of interference from the electric supply and electrical equipment on the locomotive. Since the electrified zones were among the PRR's busiest, this was a serious disadvantage.

Replacement

The trainphone system was abandoned in the 1960s as radio took over.

References

* * * {{cite book , title = Kansas City Southern in the Deramus Era , author = Marre, Louis A and Gregory J Sommers , isbn = 1-881411-14-1, lccn= 97-060478 , publisher = 1999 Withers Publishing , year = 1999 , page = 232 Pennsylvania Railroad Rail technologies