Automatic Block Signals

Automatic Block Signals. . , Automatic Block Signaling (ABS) was developed in the late 19th century to allow multiple trains to operate safely in the same direction without the risk of rear-end collision. In an ABS system, the track is divided into segments (“blocks”) and signals are placed at the ends of each block to tell train crews whether or not the track segment ahead is occupied or clear. A series of track circuits and relays operates the signals “automatically” - that is without any outside intervention. Displayed here is a pair of Union Switch and Signal Co. “Style B” lower-quadrant, semaphore signals, which were once part of the ABS system on the Southern Pacific‘s Siskiyou Line in Oregon. The signals were donated to Travel Town by Southern Pacific and restored to operation by museum volunteers. , In the days before radios and cell phones, wired telephones were provided at points along the tracks - giving train crews a “direct line” to the dispatcher. Pre-fabricated concrete telephone booths were located throughout the Southern Pacific system. The booth on display at Travel Town was originally located alongside the track between L.A. Union Station and El Monte; donated to the museum by Metrolink and restored by Travel Town volunteers. , Railroad signaling systems require constant maintenance to keep the trains running safely. In Style B signals, the semaphore blades are moved by an electric machine in the base cabinet that operates rods running up inside the mast.