Electronic key telephone systems
US4338495A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 6, 1979 |
| Grant date | Jul 6, 1982 |
| Priority date | — |
| Expiry date | Mar 6, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q3/545
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Each of the station sets in the system generates a continuous, current-modulated digital data stream carrying information concerning the status of pushbutton-actuated switches associated with a particular service or feature. This data stream is transmitted via a phantom pair over standard four-wire cable to an associated station card in the key service unit, which receives and decodes the data, implements any service requested at the associated station set by closure of a pushbutton-actuated switch in the station set, and generates a continuous voltage-modulated digital data stream carrying instructions for the connection of the station set speakerphone to either the first or second talk path formed by the first and second conductor pairs in the standard four-wire cable, for energization of light-emitting diodes associated with the pushbutton-actuated switches in the station set, and for controlling background music transmission to the associated station set. This data stream is transmitted via the aforementioned phantom pair to the station set, which receives and decodes the data and carries out the instructions contained therein. Each station card and each station set incorporate…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.