RK-400 Track circuit

RK-400 track circuit or RK-400 audio frequency track circuit manufactured by Rajman Kabir Company that has a system to determine the presence of trains on metro tracks and also to send speed codes to the ATP of the train. This system includes an audio transmitter and receiver at the same frequency. The connection to the track is by matching unit that performs impedance matching at the same frequency. Adjacent tracks are separated through insulating joints or tuning loops that include tuning units of adjacent tracks. An air core inductor is installed in the center of the tuning loop.

RK-400 circuit frequencies

RK-400 track circuit includes four frequencies 1700Hz, 2000Hz, 2300Hz and 2600Hz. These frequencies are modulated between 12 and 20 Hz in order to reduce errors related to track harmonics and other voltages close to these frequencies. Both the modulated frequencies and the main frequencies are necessary for the operation of the track circuit in the two occupied sections of the track and train speed control.

The RK-400 track circuit consists of TX transmitter, RX receiver, MU matching, TU tuning and ACI air core inductor.