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US3787621A Expired / Lapsed US ⏱️ 0.0 years remaining

Telephone set with transmission by microphone and amplifier and reception by loudspeaker

Assignee: Individual
•
Filing: 1971-08-06
•
Granted: 1974-01-22
•
Expires: 1991-08-06
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Abstract

Abstract A telephone set has sound transmission by a microphone and amplifier over a transmission circuit, and sound reception by loudspeaker over a reception circuit. Each circuit includes an input transformer and an output transformer, and both circuits are connected, through a telephone transformer, to the line. The telephone set includes an arrangement for preventing the Larsen effect and other interference between the two circuits. This arrangement includes respective sets of four diodes or transistors, connected as a Wheatstone bridge, each connected between an input transformer and the associated output transformer. A square wave multi-vibrator is connected in parallel to the output transformer of the transmission circuit and to the input transformer of the reception circuit, and is connected, through respective diodes or transistors to the input transformer of the transmission circuit and to the output transformer of the reception circuit. The multi-vibrator supplies alternating positive and negative square wave pulses, at a frequency very substantially higher than the frequency of the sound waves, to the two Wheatstone bridges, with one Wheatstone bridge receiving a positive square wave pulse at the same time the other Wheatstone bridge receives a negative square wave pulse. The multi-vibrator is continuously operative, and, in effect, chops the modulated currents in the two circuits at a very high frequency of the order of 0.5 MHz.

Inventors

  • 👤 A Barok

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-05 05:02
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/08

Claims Analysis

Total Claims: 5
Claim 1
Independent Claim 186 words
A telephone set, with sound transmission by a microphone and amplifier over a transmission circuit and sound reception by a loudspeaker over a reception circuit, comprising, in combination, two diode gates, one in said transmission circuit and the other in said reception circuit; each diode gate including a respective input transformer, a respective output transformer, and a respective set of four diodes, arranged in a ring, connecting the respective input transformer to the respective output transformer; and a control having an input connected in common to one respective input transformer and to the other respective output transformer and having two outputs, each connected to a different respective diode gate; said control supplying two distinct series of pulses; both series being composed of identical pulses but being in phase opposition with respect to each other such that a pulse will cause a gate to conduct, and the absence of a pulse will block the conductance of the gate, whereby the diode gates are blocked and opened in alternation with each other; said control supplying said series of pulses at a frequency outside the audible range of frequencies.
Claim 2
Dependent Claim 186 words
A telephone set, with sound transmission by a microphone and amplifier over a transmission circuit and sound reception by a loudspeaker over a reception circuit, comprising, in combination, two diode gates, one in said transmission circuit and the other in said reception circuit; each diode gate including a respective input transformer, a respective output transformer, and a respective set of four diodes, arranged in a ring, connecting the respective input transformer to the respective output transformer; and a control having an input connected in common to one respective input transformer and to the other respective output transformer and having two outputs, each connected to a different respective diode gate; said control supplying two distinct series of pulses; both series being composed of identical pulses but being in phase opposition with respect to each other such that a pulse will cause a gate to conduct, and the absence of a pulse will block the conductance of the gate, whereby the diode gates are blocked and opened in alternation with each other; said control supplying said series of pulses at a frequency outside the audible range of frequencies.
Claim 3
Dependent Claim 93 words
A telephone set, as claimed in claim 1, in which said control comprises a multi-vibrator having input terminals connected, in parallel, to the midpoint of the primary winding of the output transformer of said transmission circuit and to the midpoint of the secondary winding of the input circuit of said reception circuit; said multi-vibrator having two outputs, one connected to the midpoint of the secondary winding of the input transformer of said transmission circuit and the other connected to the midpoint of the primary winding of the output transformer of said reception circuit.
Claim 4
Dependent Claim 26 words
A telephone set, as claimed in claim 2, including a respective diode connected in series between each output of said multi-vibrator and the associated transformer winding.
Claim 5
Dependent Claim 16 words
A telephone set, as claimed in claim 3, in which said multi-vibrator supplies square wave pulses.

References Cited (Backward Citations)

US3046354A Cited
US3594507A Cited
US3665106A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1977-01-21 1977-07-23 1978-01-22 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1981-01-21 1981-07-23 1982-01-22 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1985-01-21 1985-07-23 1986-01-22 $7700.00 Window Closed / Lapsed

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