This section is from the book "Amateur Work Magazine Vol6". Also available from Amazon: Amateur Work.
The attention of railroad men has been attracted to the telegraph railroad signal for the manufacture of which the Telegraph Signal Company has been organized at Rochester, N. Y. The signal is the invention of Selden R. Whight, a railroad telegrapher. It is essentially an emergency device, primarily for use on single track railroads, and is intended to place the control of semaphores at the several stations under the control of the dispatcher. By means of this signal the dispatcher may throw a semaphore to 'stop position" at any desired point, regardless of the condition of the operator's instrument at that station, that is, whether or not the key of his instrument on the dispatcher's wire is open. The signal instruments form part of the operator's apparatus at each station, the relay being used to operate the semaphores and bell signal. The signal devices at all stations are identical. Each instrument is provided with an accurate and unfailing selector which enables the operator to select not only the required station but the particular semaphore winch he wishes to operate. For each station there are three contacts on the selector drum-one for the first semaphore, one for the second and one for a bell signal.
Briefly, the signal operates in this way: If the dispatcher wishes to throw, say, the east bound semaphore at a station he would hold the key of his instrument open 50 sec. At the expiration of 40 sec. a contact would be made which would cut out the keys at every instrument on the circuit. At the end of 50 sec. contact would be made through another contact point, which would enable the dispatcher to operate the selector. By means of his key the dispatcher would step the selector to the number of the semaphore which he had selected to throw and wait 20 sec. At the end of that period the semaphore would be thrown to "stop position," and a messenger call signal would apprise him of the fact. Closing the key a few seconds later would restore all of the signal devices at all of the stations to normal, leaving the interlocking semaphore to be drawn to safety position when everything was clear. The other semaphore or bell signal would be operated in a similar way.
 
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