Locomotive inductive signalling system - has current sensing relay with level detector and trigger operating bistable to increase sensitivity

摘要

The railway locomotive inductive pick-up circuit for safety signalling systems comprises an AC generator connected to a power amplifier (2). The amplifier output is fed via the primary of a current transformer (41) to the locomotive magnet (3). The magnet circuit (31, 32) is tuned to the generator frequency, and fed with constant current. The amplifier output is directly connected to a trigger circuit (5) which gives an output pulse whenever the input falls below a set value. A second trigger circuit (6) connected to the current transformer secondary (42) gives an output pulse whenever the input current exceeds the norm. The trigger circuits outputs are connected to the set and reset inputs respectively of a 2-Bit shift register (7) and a bistable (KE) provides the start control. The register output is amplified to operate the relay (9).