DISPOSITIVO PER IMPIANTI TELEFONICI,SPECIE PER IMPIANTI TELEFONICI DERIVATI,IN CUI VIENE VALUTATO UN SECONDO SEGNALE ACUSTICO TRASMESSO A RITROSO(SEGNALE ACUSTICO INTERNAZIONALE)

A telephone system has central and decentralised contol appts. and a traffic link between identical and different installations, one such installation being associated with a coupling network which provides links between decentralised control apparatus, and a central control with information transmission line network and a central audible signal receiver for evaluation of audible signs appearing by way of a call-office. After occupation of a set of link lines and selection of an indicator or separation prefix evaluated by a central control and received by way of a selection set, the connection of a central audible sign receiver at the call line link is initiated as is the prevention of retransmission of the call selection subsequently selected and appearing by way of the link line set, and their intermediate storage in a particular memory. After reception of an audible sign appearing by way of the occupied link line set ad evaluated by the audible signal receiver, the retransmission of the stored call selection is controlled from the central control.