Re: Telegraph Components

Answers to John Cole's questions:

Normal telegraph circuit terminal voltages on railroad lines were typically supplied by The Western Union nearest main office, or from WU maintained rectifiers at terminal points where a local WU office was located.

Typical terminal voltages applied at each end of a circuit were 160, 110 or 80 Volts DC, depending on the circuit particulars required. Opposite poles of Battery were applied at each end of the circuit, with the opposite end of the supplies connected to Earth. The total terminal voltage applied to most circuits was split between the terminal ends for reasons of improved operation of the circuit during wet weather high leakage (current escape over wet insulators or trees and brush contacting the wires) conditions.

Normal operating current in mainline circuits equipped with 120 or 150 Ohm mainline instruments (relays or mainline sounders) was on the order of 40-60 Milliamperes. with 50Ma. being an average. Local circuits operating in the offices equipped with local sounders were typically operated at 250 Ma..(4 Ohm Gravity battery instruments) or 35 Ma. (400 Ohm instruments fed with rectifiers from commercial mains).

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