Automatic telephone subscriber identification appts. - has digital correlation detector rapidly sensing off hook condition of subscriber lines

摘要

The automatic subscriber identification appts. is suitable for use with a telephone exchange network (1). The exchange is connected between trunk (3) and subscriber lines (2) and the appts. comprises an off hook condition detector (5) on one of the trunk lines connected to the appts. A feedback path exists between the trunk lines (3) and the subscriber lines (2). The feedback signal is digital, and the tester comprises a digital correlation detector connected to each subscriber line. One input receives a subscriber line signal, and the second receives a digital test signal corresponding to the feedback, the detector comparing their polarities.