Multifrequency signal receiver
US4091243A · kind A · utility
11Cited by
1References
9Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Jul 26, 1977 |
| Grant date | May 23, 1978 |
| Priority date | — |
| Expiry date | Jul 26, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/453
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Detection of valid two-out of-N multifrequency signals is realized by employing a microprocessor in conjunction with a controllably adjustable or settable reference threshold level and a plurality of threshold detectors. Under control of the processor, a reference threshold level supplied to the detectors is set to a first prescribed level. Upon detection of a tone which exceeds the first threshold level the processor controllably sets the reference threshold level to a second prescribed level. Detection of two, and only two, tones which are present for at least a minimum prescribed interval are then considered valid.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.