Circuit arrangement for determining the connection condition of a subscriber line in a telecommunications network

US4320260A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventor

• Robert Lechner · Otterfing, DE

Key dates

• Filing date: Sep 9, 1980
• Grant date: Mar 16, 1982
• Expiry date: Sep 9, 2000

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04M3/2272
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

A circuit arrangement for determining the connection condition of a plurality of subscriber lines in a telecommunication network, each of the subscriber lines having two wires extending between a subscriber station and a subscriber line interface circuit and being connected via respective resistors to the two poles of a DC voltage source. For a group of such subscriber lines the operating conditions are consecutively monitored by sampling the voltage occurring at two sampling points of both wires by a respective multiplexor and passing it to a comparator having inputs which are temporarily inter-connected by filter capacitors each separately associated with a respective subscriber line interface circuit. In addition, the comparator receives a reference voltage determining a threshold voltage. For ground key indication one of the sampling points is connected to one input of a further comparator which second input is supplied by a corresponding further reference voltage. The output signals of both comparators are presented at a central control unit for evaluation. When monitoring a ground key indication the output signal of the second comparator, however, is passed only if presuppose…