Intercom call signaling mechanism
US3978468A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Nov 11, 1974 |
| Grant date | Aug 31, 1976 |
| Priority date | — |
| Expiry date | Nov 11, 1994 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M11/025
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
The master unit of an intercom in a building includes a digital code selector operating a digital coder for transmission of remote unit identification code signals to the intercom receivers of several remote units for alerting persons at such respective units. Each remote unit includes a receiver for receiving both conversation transmission and an identification code signal, reference signal means and a signal comparator for comparing identification code signals received by its receiver with its reference identification code signal. Reception by a remote unit of the appropriate identification code signal conditions its receiver to produce an audible call or alerting signal from an electronic call signal received by the receiver of that remote unit from the transmitter of the master unit. The call signal is generated electronically and supplied to the transmitter of the master unit for transmission to all of the remote units. Both the conversation transmission and the indentification code signals are transmitted over the conventional electrical power wiring of the building.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.