US4481677A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical transmitting and receiving apparatus
Assignee: Nortel Networks Ltd
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Filing: 1983-01-31
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Granted: 1984-11-06
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Expires: 2003-01-31
Abstract
Abstract Speech signals are optically coupled from a transmitter to a receiver using low duty-cycle infrared pulses. A conditioning circuit converts an a.c. input signal to be transmitted into a unipolar signal, whose magnitude controls the frequency of an oscillator which determines the frequency of the infrared pulses. In the receiver the detected pulses are low-pass filtered in a voice-band filter the output of which is coupled to a telephone line and/or a loudspeaker. A plurality of similar transmitters can be provided to enable signals from an arbitrary number of people to be coupled to a common receiver.
Inventors
- 👤 Yuan-Lu Li
- 👤 Leslie J. Crane
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 07:12
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/11; H04B10/114; H04B10/1143; H04B14/00; H04B14/02; H04B14/026
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
137 words
Optical transmitting and receiving apparatus comprising: oscillator means for producing an output signal at a controllable frequency; control means for controlling said frequency in dependence upon the amplitude of a signal to be transmitted; means responsive to said output signal for emitting optical pulses at the controlled frequency; means for detecting the optical pulses; filter means for low-pass filtering an output of the detecting means to produce a received signal; wherein the signal to be transmitted comprises an a.c. input signal and the control means comprises: means for rectifying the input signal; peak-detecting means responsive to the rectified input signal to produce a d.c. signal in dependence upon the peak amplitude of the rectified input signal; and summing means for summing the d.c. signal and the input signal to produce a unipolar signal for controlling said frequency.
Claim 2
Dependent Claim
137 words
Optical transmitting and receiving apparatus comprising: oscillator means for producing an output signal at a controllable frequency; control means for controlling said frequency in dependence upon the amplitude of a signal to be transmitted; means responsive to said output signal for emitting optical pulses at the controlled frequency; means for detecting the optical pulses; filter means for low-pass filtering an output of the detecting means to produce a received signal; wherein the signal to be transmitted comprises an a.c. input signal and the control means comprises: means for rectifying the input signal; peak-detecting means responsive to the rectified input signal to produce a d.c. signal in dependence upon the peak amplitude of the rectified input signal; and summing means for summing the d.c. signal and the input signal to produce a unipolar signal for controlling said frequency.
Claim 3
Dependent Claim
35 words
Apparatus as claimed in claim 1 wherein the oscillator means comprises a frequency-controlled oscillator and a monostable stage for producing low duty-cycle pulses, constituting said output signal, in response to an output of the oscillator.
Claim 4
Dependent Claim
33 words
Apparatus as claimed in claim 2 and including means responsive to power being initially supplied to the transmitting apparatus to inhibit production of said pulses by said monostable stage for a predetermined period.
Claim 5
Dependent Claim
20 words
Apparatus as claimed in claim 1 wherein the means for emitting optical pulses comprises a plurality of infrared light-emitting diodes.
Claim 6
Dependent Claim
14 words
Apparatus as claimed in claim 1 wherein the rectifying means comprises a full-wave rectifier.
Claim 7
Dependent Claim
31 words
Apparatus as claimed in claim 1 and including means for applying a d.c. bias to the summing means, thereby to suppress input signals having an amplitude less than a threshold level.
Claim 8
Dependent Claim
71 words
Apparatus as claimed in claim 1 wherein the peak-detecting means comprises: a capacitor; means for charging the capacitor to a voltage which is dependent upon the peak amplitude of the rectified input signal; means for discharging the capacitor at a first, relatively slow, rate; and means, responsive to the voltage to which the capacitor is charged falling to a predetermined value, for discharging the capacitor at a second, relatively rapid, rate.
Claim 9
Dependent Claim
36 words
Apparatus as claimed in claim 1 and including a microphone and amplifying means responsive to an output signal from the microphone to produce said a.c. input signal, wherein the filter means comprises a low-pass voice-band filter.
Claim 10
Dependent Claim
35 words
Apparatus as claimed in claim 1 and comprising a plurality of independent transmitting apparatus and a common receiving apparatus, each transmitting apparatus comprising a said oscillator means, control means, and means for emitting optical pulses.
Claim 11
Dependent Claim
19 words
Apparatus as claimed in claim 1, wherein an output of the filter means is coupled to a telephone line.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-11-06 | 1988-05-07 | 1988-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-11-06 | 1992-05-07 | 1992-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-11-06 | 1996-05-07 | 1996-11-06 | $7700.00 | Window Closed / Lapsed |