| 摘要 |
The invention concerns an arrangement in a telex transmission system, in which signals are exchanged in both directions between a subscriber and an exchange across a single pair of wires, for detecting which of the parties is signalling at the moment. The invention utilises the circumstance that both current and voltage are interrupted when signalling from the exchange, while when signalling from the subscriber only the current is interrupted. The invention is characterised in that it contains a detection circuit DC consisting of an electronic circuit EC and a relay CS. The detection circuit detects the voltage on the conductor in the connection where the interruption occurs. When signalling from the subscriber, the circuit DC is energised by the voltage remaining on said conductor so that a resting position signal is put out from said electronic circuit EC to the relay CS, and when signalling from the exchange as a consequence of the loss of voltage upon interruption a reset signal is put out from the electronic circuit EC to the relay CS. The signals from the relay CS alternately break and make a circuit belonging to an indicator element M. The indicator element consists of the colour shifter in a co-plotter connected to the detection circuit DC, wherein upon receiving the resting position signal it remains in the original state and records with a colour, such as black, which corresponds to signalling from the subscriber, but upon receiving the reset signal it changes state and records with a different colour, such as red, which corresponds to signalling from the exchange. <IMAGE> |
