Circuit arrangement for displaying subscriber line seizures by ancillary devices on the associated digital telephone station

摘要

The invention relates to a circuit arrangement for displaying subscriber line seizures by ancillary devices in digital telephone systems. The intended object is to identify on the associated telephone station whether the subscriber line has been seized by the ancillary device. This display is intended to be possible independently of any special contact which may be provided in the ancillary device. To achieve this, a loop monitor, which in each case inserts a loop indicator into one wire of the subscriber line to both the telephone system and the associated telephone station, is inserted upstream of the ancillary device. If only the telephone system indicator identifies loop current, a signal is transmitted by the ancillary device as an indication of seizure through the actuation of a contact of the telephone system which transmits a corresponding digital signal to the telephone station. The invention is used in all digital telephone systems with ancillary devices on the subscriber lines. <IMAGE>