Telephone regulator circuitry

Details Telephone regulator circuitry Telephone regulator circuitry

1982-04-23

1985-01-22

George, Keith E.

179 16F, H04M 176

Patent

active

044953828

ABSTRACT:
This invention provides a single integrated circuit device which replaces the non-integrated "encapsulated circuit" of the standard prior art telephone set. The circuit of this invention achieves proper D.C. regulation of the telephone line, by presenting one of several possible D.C. impedances to the telephone line when the telephone set is in the off-hook condition. The circuit of this device provides such regulation by varying the gain relationship of the telephone set for various distances from the central switching office, thereby maintaining a rather uniform signal amplitude in a plurality of telephone sets located at various distances from the central switching office. In one embodiment, this is done using a novel regulator substantially completely formed as part of a single integrated circuit chip containing a receiver amplifier, transmitting amplifier, dialing circuitry and ringing circuitry. The use of integrated circuit technology allows many of the circuit components to be formed in a balanced manner thereby substantially improving the audio quality achieved with this invention compared to prior art telephone sets. The transmitter amplifier of this invention allows the use of a number of different microphones, including the standard telephone carbon microphone. In one embodiment of this invention the microphone used is an electret. The transmitter amplifier of this invention provides wide dynamic range and low distortion, while obtaining its power requirements from the telephone line itself. The power requirements of the transmitter amplifier of this invention are minimal, with the transmitter amplifier of this invention being capable of operating with as little as two volts difference between the speech line and the reference potential. The receiver amplifier of this invention provides a differential output voltage for driving the receiver transducer. In this fashion, DC blocking to the earpiece is not required, thereby eliminating the need for a rather expensive and bulky DC blocking capacitor.

REFERENCES:
patent: 3989902 (1976-11-01), Cowpland
patent: 4143247 (1979-03-01), Yoshitoshi et al.
patent: 4332984 (1982-06-01), Davis et al.
patent: 4360710 (1982-11-01), Chaput et al.
patent: 4388498 (1983-06-01), Geboers et al.
patent: 4400588 (1983-08-01), Stobbs et al.
Erratico et al., "The First Electronic Speech Circuit Opens the Way to the Fully Electronic Telephone", IEEE Transactions on Consumer Electronics, vol. LE-26, Feb. 1980, pp. 73-80.
American Microsystems, Inc., "S2559 A/B/C/D Tone Generator", Jan. 1979, (Brochure).
American Telephone and Telegraph, "Electrical Characteristics of Bell System Network Facilities at the Interface with Voiceband and Ancillary and Data Equipment", Preliminary Bell System Communications Technical Reference, Aug. 1976.

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