Telecommunication subscriber line access circuit with ground key and insulation fault indication
US4301334A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 6, 1980 |
| Grant date | Nov 17, 1981 |
| Priority date | — |
| Expiry date | Mar 6, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/38
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A subscriber line access circuit for use in a telecommunications system is disclosed. The subscriber line access circuit has a power supply bridge in the form of a first resistor inserted in the b-wire (ground potential side) of a subscriber line, a second resistor inserted in the a-wire (supply potential side) of the subscriber line, and a capacitor which bridges the two wires at the terminals of the two resistors on the sides thereof opposite to the respective potential sources. This supply bridge is coupled on the capacitor side with a two-to-four wire hybrid transformer for the two-wire/four-wire transition to the system, and includes an evaluating circuit which delivers an indicating signal when the subscriber actuates a ground key. A cutoff circuit is arranged in the power supply bridge in series with the first or the second resistor, or both, between such resistor and the winding of the hybrid transformer to which it, the resistor, as well as the evaluating circuit are connected. This cutoff circuit comprises a cutoff switch which is opened, with a delay, upon ground key actuation and closed when the ground key actuation is terminated.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.