CIRCUIT ARRANGEMENT FOR BLOCKING A BIDIRECTIONAL AMPLIFIER AGAINST RECEIVING OUTGOING SIGNALS

摘要

A circuit for the reciprocal transmission of signals through transmitting channels. The circuit has amplifiers therein for amplifying the signals being transmitted in opposite directions along the line. A pair of branch determining circuits are provided so that the signals which are emitted by one amplifier and which must be transmitted in one direction do not overdrive the input of a further amplifier which is provided for amplification of signals to be transmitted in the other direction. A circuit is provided in each of the branch determining circuits for the continuous production of a reference signal which is fed to a comparator circuit connected to the input of the amplifier so that the signals arriving at the amplifier can be compared with the outgoing signals that are being transmitted in the opposite direction. The reference voltage is controlled with respect to its magnitude and phase so that it corresponds to the voltage produced by the outgoing signals and any difference existing between the reference voltage and the outgoing signals will cause the comparator circuit to produce a signal to effectively prevent the outgoing signals from reaching the input to the amplifier.