Tone detector
US4042788A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 17, 1976 |
| Grant date | Aug 16, 1977 |
| Priority date | — |
| Expiry date | May 17, 1996 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/457
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A digital tone detector is of the period detection type employing a digital counter which is stepped by means of a high speed clock. The counter is reset by zero-crossings of an analog tone signal. A set of period range decoder gates indicate the presence of any of a set of predetermined frequency tones. A .div. 4 counter is introduced between the terminal which receives the zero-crossing signal and the reset input of the counter. Sequence control circuits are provided to coordinate the timed relationship of readout and initiation of a new detection period such that the speed of response is minimally degraded by the .div. 4 counter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.