Modern signaling on the reading railroad

MOST modern signal systems have many features of interlocking and signal control that are common to each other. A description of the signal system on one railroad, therefore, may be of interest to others. Following a brief outline of the earliest forms of signaling employed on the Reading Railroad, this paper describes the Reading's most recent installation of 100-cycle a-c color light signaling. The 100-cycle frequency was first used in the continuous coded train control territory, where a distinctive frequency was required to eliminate any possibility of foreign inductive interference, and was later adopted for use in electrified territory, as the range between the 100-cycle signal frequency and the 25-cycle electrification frequency permitted the use of frequency selective track relays.