PROCEDIMENTO E DISPOSITIVO PER LA IDENTIFICAZIONE AUTOMATICA DELLO UTENTE CHIAMANTE IN CENTRALI TELEFONICHE PASSO A PASSO

To automatically identify a calling subscriber, the seizure of a first group selector is recognized, a voltage easy to distinguish from the other signaling criteria used in the exchange is applied to that selector and the presence of said voltage on the metering wire in correspondence with the meter is recognized by comparing with suitable thresholds the voltages present on the metering wires of all the subscribers connectable to that selector. Once the presence of that voltage on a wire has been recognized the group selector is disconnected from the identification voltage source.