Circuit arrangement for identifying telephone subscribers

Abstract

A request generator, when operated by a telephone subscriber or by a processor at an exchange, briefly interrupts an established talking connection to send a trigger signal toward a participating station for activating an identity transmitter associated therewith to send back a characteristic code individually assigned to that station. The code, which may consist of up to 16 bytes, is fed to an identity receiver at the inquiring station or at the exchange for visual display and/or recordal. A subscriber's request generator is preferably disposed downstream of the corresponding identity transmitter, as seen from the subscriber station, and responds to an activating signal emitted by that subscriber with a frequency outside the voice band for sending out the trigger signal, thereby preventing a response to this identity transmitter. In the event of two subscribers sharing a common party line, a read-only memory in the identity transmitter of that line stores only one code but a logic network in its readout circuit modifies a predetermined bit of one byte, and if necessary a corresponding parity bit in a check word of the code, if the line is seized by a particular one of the two subscribers. When the establishment of a talking connection is controlled by a processor at the exchange, a centralized identity transmitter may have a read/write memory loaded by the processor with the characteristic code of a participating subscriber station and send it out in response to a trigger signal from a request generator at the exchange or at the other participating station.