Preferential TDM carrier transmission system for order telegrams - uses priority identification switch in conjunction with AND=OR logic gates liberating transmitter function

Each transmitter is controlled by a transmission time generator and HF detector (pref. squelch filter). Fixed-frequency pulses trigger the transmission of an order telegram via an AND gate and OR gate only when no HF is detected. A monitor circuit inhibits the HF detector after a delay of about 100 to 200 ms. The transmitter is triggered only if the detector has emitted no signal for a min. duration of at least two chain lengths (50 to 75 ms). A counter counts the number of inhibitions of transmission by the HF detector, and is reset to zero by an end-of-transmission switch. The priority switch, memory AND and OR gates override the generator when necessary in favour of another transmitter.