Combined encoder and decoder circuit
US4001782A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 6, 1975 |
| Grant date | Jan 4, 1977 |
| Priority date | — |
| Expiry date | Nov 6, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04W88/188
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A combined encoder and decoder circuit which uses a single frequency selective resonant reed in a closed loop oscillator configuraion permitting simultaneous encoder and decoder operation. A closed loop oscillator has a resonant reed connected in series between an input and output terminal and produces a signal at the resonant frequency of the reed. Positive signal feedback from the output to input terminal is provided by an amplifier, operated between saturation and cut-off, and a controllable attenuator. A level detector and the attenuator effectively form a limited range negative feedback loop which effectively maintains the signal magnitude at the output terminal at a substantially constant level. A decode detector monitors the signal level at the output terminal and produces a decode signal when an input signal, having the same frequency as the resonant frequency of the reed, has a magnitude which is so large that the negative feedback circuitry cannot maintain a constant signal level at the oscillator output terminal. The output of the positive feedback amplifier always provides a constant amplitude output signal which can be used for encoding purposes. Because of the use of …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.