Abstract: A telephone office is provided with a dedicated trunk modified to transmit to subscribers lines connected to the same office the multifrequency tones from an out-going sender used to identify the calling party. Provision is made for connecting a subscriber's line pair to the dedicated trunk on provision across the pair of a special access code of pulsed or dialled digits. The dedicated trunk is designed to provide the necessary signals to cause the out-going sender to perform its functions. A test set is provided for connection to a subscriber's line pair to dial the special access code. The test set first tests for line conditions before dialling. After dialling the test set detects the information in the multi-frequency tones originating with the outgoing sender. At the telephone office an outgoing sender is preferably modified to send, in addition to the number of the calling party, the line location address of his pair of lines. The test set also detects this information.