Cab Signals: Introduction and Types
Perhaps cab signals ought to be placed with special signal forms (staff, tickets and tokens in Appendix I) rather than with regular signals because carried aboard the train. However, the message systems are often patterned after those of wayside signals and in some cases the signals are miniature versions of wayside signals, and even numerical forms produce conventional messages though without color intermediaries and are therefore placed with the regular signals.
Information on cab signals is sketchy. Even full-scale codes may not mention cab signals. Journal and trade literature is often a better information source than signal codes. The available information is sufficient, though limited, to suggest something of cab signal forms. Cab signals seemingly have three general forms: a) color-light signals, b) position-light signals, and c) numerical signals (which in turn includes some color indication forms).
Cab signals are frequently not "stand-alone systems." Some are used in conjunction with wayside signals; others with some form of automatic train control or train warning systems. Since this study concentrates on signals and messages it will not take up the subject of АТС and other related systems of train control, nor with cab-signal-track delivered signal control impulses. There are three systems for delivering operational impulses to the signals: the continuous, the intermittent and a composite version (Fratassi (1977, 193; see also Union Switch and Signal 1984) .
Major users of cab signals include the U.S., USSR, Japan, West Germany, Italy and France. URO has also studied this form of signalling. With the increase of high-speed trains, especially in Europe, expansion of cab signalling may increase in significance.
