Hold detecting and control circuit for a key telephone system
US4803718A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 6, 1987 |
| Grant date | Feb 7, 1989 |
| Priority date | — |
| Expiry date | Mar 6, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M9/002
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A key telephone system for use with at least two telephone lines that extend between a central office and two or more telephone stations. Each station is capable of responding to a manually-actuated hold select switch by establishing a hold condition on one of the lines and by connecting a line terminating impedance across the line that is to be held. Each station is further capable of monitoring the state of each line, and indicating the state of each line, without applying any indicating signals to the telephone lines. Each station furthermore determines threshold voltages for on-hook, off-hook and hold line states and determines line state by comparison of line voltage with such threshold voltages.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.