Telecommunication line switching circuit
US4063045A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 27, 1976 |
| Grant date | Dec 13, 1977 |
| Priority date | — |
| Expiry date | Jul 27, 1996 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L25/26
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An isolated line switching circuit for direct connection of a telephone, teleprinter, or like telecommunication instrument to a transmission line, comprising a solid-state optical cell including a light-actuated optical receiver that generates an electrical current when illuminated by an associated light-emitting device (LED), and a switching transistor having its emitter-collector discharge path connected in series with the transmission line; the optical receiver is connected to the base and emitter of the transistor to drive the transistor conductive when the LED is energized by an actuation signal initiated in response to a ring signal. A high-resistance emitter-to-base circuit for the transistor drains the collector leakage current (I.sub.CBO) and maintains a high off resistance even at high temperatures.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.