Abstract: The invention relates to a circuit for a telephone station which is mains-supplied or remote-powered as required, i.e. in the event of a mains failure an automatic switchover from the mains voltage to remote power takes place, and a switchover in the opposite direction takes place when power is restored. This is effected without any additional voltage insulation and without substantial additional expense.This is achieved in that a switching regulator which establishes the actual feed voltage is connected to the mains DC voltage, where a blocking voltage for a transistor located in the remote feed unit is obtained from the mains DC voltage. If the mains fails, the blocking voltage for the transistor is also lost and the latter is switched through by the remote feed voltage which acts upon its base. This procedure is automatically reversed when the main voltage again becomes available.