System for simultaneous analog and digital communications over an analog channel
US5410541A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 4, 1992 |
| Grant date | Apr 25, 1995 |
| Priority date | — |
| Expiry date | May 4, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/57
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
At a transmitting end, frequencies used to a construct a digital signal are substantially removed from an analog signal by a notch filter circuit to produce an interim signal which is then combined with the digital signal as by combining to produce a composite analog signal that is transmitted to a receiving end. At the receiving end the frequencies used to construct the digital signal are substantially removed from the composite analog signal by a notch filter circuit. In this way the digital signal can be transmitted simultaneously with the analog signal without errors that could be introduced by the analog signal, and with only a slight change to the frequency spectrum of the analog signal. This can be used in telephone communications for sending caller ID digital data over the same line carrying a voice signal. Caller ID data is sent FSK encoded and only those frequency used for the mark and the space are attenuated in the received voice signal before it reaches the telephone's speech circuit. For PSK encoded data method, a single notch filter removes the carrier frequency from the voice signal at the receiving end. In this way, the user is not subjected to the audible frequenc…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.