Programmable multifrequency tone receiver
US4354248A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 28, 1979 |
| Grant date | Oct 12, 1982 |
| Priority date | — |
| Expiry date | Nov 28, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/30
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A multifrequency tone receiver is disclosed for detecting simultaneous tone signals in a sampled digital signal. The tone receiver includes a microprogrammed sequence controller, a time-multiplexed digital filter and a signal processing microcomputer. For each sample of the digital signal, the sequence controller is programmed to time multiplex the digital filter for performing three cascaded second order filtering operations (two bandpass filter operations and one low pass filter operation) for each of six tone signals to provide corresponding energy estimates and one additioal filtering operation to provide a total energy estimate. The signal processing microcomputer processes a number of sets of the seven energy estimates and provides an indication when a multifrequency toner pair has been detected. The digital filter, when enabled by a filter start signal from the sequence controller, asynchronously performs a single multiplication-like filtering operation to implement each second-order filter, and provides a filter done signal upon completion of the filtering operation. Full-wave rectifying capability is provided during low pass filtering operations by logically complementing …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.