Multifrequency receiver
US4227055A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 7, 1978 |
| Grant date | Oct 7, 1980 |
| Priority date | — |
| Expiry date | Dec 7, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/453
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Reception of valid two-out-of-N incoming multifrequency signals is realized by employing a multifrequency detector (FIG. 1, 102) including a plurality of filters (FIG. 2, 202-1through 202-N) and a corresponding plurality of comparators (206-1 through 206-N). The comparators are jointly responsive to output signals from the filters and to a threshold level (RMS REF) dynamically generated (via 204) in response to the incoming signal for generating output pulse signals (103-1 through 103-N) representative of multifrequency tones which exceed the threshold level (RMS REF). The pulse signal outputs (103-1 through 103-N) from the multifrequency detector (102) are evaluated (by 105) to determine whether two and only two tones are present which meet a prescribed criteria. The criteria is that each tone be present for at least a predetermined minimum portion of a prescribed sampling interval and that both tones be present for at least a predetermined number of consecutive sampling intervals. Out-of-band signals are rejected while increasing receiver sensitivity to inband signals by maintaining the peak amplitude of outputs from the filters generated in response to a single tone incoming sig…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.