Alternating voltage system for railway signalling - uses alternating voltage generator coupled to pickup brush on locomotive

摘要

Use of alternating voltage for transmitting signals on a railway system enables a greater amount of information to be transmitted to and from a locomotive when compared with a direct current system. An alternating voltage generator (6) generating at a particular frequency is transformer coupled (7) to a circuit (8) attached to a pick-up brush (3). This circuit contains a current detector comprising a transformer (9) with receiving circuits (10) controlling relays. A crocodile circuit (2) is connected to a change over switching circuit (4) followed by a tuned circuit (11) preventing flow of ac. When a relay contact (13) in an earthing circuit (12) closes current in a diode (14) provides one signal for a receiver (10). A contact (18) in a second circuit (17) provides a second signal.