US3780228A — Automatic disconnect circuit for reducing dial pu…

Claim 1

Independent Claim 324 words

Apparatus for automatically disconnecting a local subscriber carrier battery charging circuit that is connected through a cable pair to a central office power source from the latter, for a prescribed time interval, after initiation of a dial pulse by a telephone of a physical circuit, for reducing dial pulse distortion comprising: first means for selectively connecting the charging circuit to the cable pair and thus to the power source, said first means comprising a first transistor having collectoR and emitter electrodes connected in series between a line of the cable pair and a first input terminal of the charging circuit, and having a base electrode; a first semiconductor diode having one terminal connected to said first transistor base electrode; and second means connecting the other line of the cable pair to a second input terminal of the charging circuit; third means for detecting a transient voltage occurring on the cable pair on initiation of a dial pulse in the telephone of the physical circuit, the transient voltage being of a limited duration that is much less than the duration of the dial pulse; and fourth means responsive to operation of said third means for opening said first means at the start of the dial pulse and holding said first means open to disconnect the local battery charging circuit from the central office power source for a prescribed time interval, that is greater than the duration of the transient voltage, following detection of initiation of the dial pulse, said fourth means comprising a first resistor, a first capacitor, and fifth means connecting said first resistor and first capacitor in series across the cable pair with the junction of said first resistor and first capacitor connected to the other terminal of said first diode. the charge on said first capacitor from the central office power source maintaining said first transistor conducting during quiescent conditions prior to the telephone of the physical circuit producing a dial pulse.

Claim 2

Dependent Claim 324 words

Apparatus for automatically disconnecting a local subscriber carrier battery charging circuit that is connected through a cable pair to a central office power source from the latter, for a prescribed time interval, after initiation of a dial pulse by a telephone of a physical circuit, for reducing dial pulse distortion comprising: first means for selectively connecting the charging circuit to the cable pair and thus to the power source, said first means comprising a first transistor having collectoR and emitter electrodes connected in series between a line of the cable pair and a first input terminal of the charging circuit, and having a base electrode; a first semiconductor diode having one terminal connected to said first transistor base electrode; and second means connecting the other line of the cable pair to a second input terminal of the charging circuit; third means for detecting a transient voltage occurring on the cable pair on initiation of a dial pulse in the telephone of the physical circuit, the transient voltage being of a limited duration that is much less than the duration of the dial pulse; and fourth means responsive to operation of said third means for opening said first means at the start of the dial pulse and holding said first means open to disconnect the local battery charging circuit from the central office power source for a prescribed time interval, that is greater than the duration of the transient voltage, following detection of initiation of the dial pulse, said fourth means comprising a first resistor, a first capacitor, and fifth means connecting said first resistor and first capacitor in series across the cable pair with the junction of said first resistor and first capacitor connected to the other terminal of said first diode. the charge on said first capacitor from the central office power source maintaining said first transistor conducting during quiescent conditions prior to the telephone of the physical circuit producing a dial pulse.

Claim 3

Dependent Claim 115 words

Apparatus according to claim 1 wherein said third means comprises a second transistor having a base electrode, and having collector and emitter electrodes connected across said first capacitor, a second resistor, a second capacitor, said second resistor and second capacitor being connected in series between the one line of the cable pair and said second transistor base electrode, and sixth means connected across said second transistor base-emitter junction for discharging said second capacitor, said second transistor conducting during a transient line voltage on initiation of a dial pulse for discharging said first capacitor to cut off said first transistor until said first capacitor charges to a level to again bias and first transistor into conduction.

Claim 4

Dependent Claim 15 words

Apparatus according to claim 2 wherein said sixth discharging means comprises a second semiconductor diode.

Claim 5

Dependent Claim 70 words

Apparatus according to claim 3 wherein said fourth means comprises a third capacitor connected between said first transistor output electrode that is connected to the charging circuit and said second connecting means, and a fourth capacitor bypassing said first transistor base-emitter junction for causing said first transistor to simulate an inductor during conduction thereof, said third capacitor and first transistor operating as a low-pass filter during conduction of the latter.

Claim 6

Dependent Claim 34 words

Apparatus according to claim 4 wherein the values of said first resistor and first capacitor are selected to maintain said first transistor conducting in the linear region and out of saturation during conduction thereof.

Claim 7

Dependent Claim 115 words

Apparatus according to claim 5 wherein said second connecting means comprises a third transistor having collector and emitter electrodes connected in series between the other line of the cable pair and the second input terminal of the charging circuit and having a base electrode, and a third diode having one terminal connected to said third transistor base electrode and the other terminal connected to said first capacitor terminal that is spaced from said first transistor, and said fourth means including a fifth capacitor connected across said third transistor base-emitter junction and a third resistor connected between said third transistor collector electrode and the other terminal of said third diode for producing a symmetrical disconnect circuit.

Claim 8

Dependent Claim 272 words

A two-port network for disconnecting a local subscriber battery charging circuit fRom a cable pair and a central office talking battery for a prescribed time interval after initiation of a dial pulse by a telephone of a physical circuit, comprising first and second switching transistors having emitter electrodes connected to different terminals of the output port, having collector electrodes connected to different terminals of the input port, and having base electrodes, first and second resistors, a first capacitor, first connecting means connecting said first resistor, first capacitor, and second resistor in series across the input port and connecting the respective junctions of said first capacitor with said first and second resistors to the base electrodes of said first and second switching transistors, respectively, a third transistor having collector and emitter electrodes connected to opposite terminals of said first capacitor and having a base electrode, a second capacitor, second connecting means connecting said second capacitor between one terminal of the input port and said third transistor base electrode, and third means connected across the base-emitter junction of said third transistor for discharging said second capacitor, said first and second switching transistors conducting to pass a charging current from the talking battery prior to the physical circuit telephone producing a dial pulse, said third transistor being responsive to a transient voltage on the leading edge of a dial pulse that is impressed across said second capacitor for discharging said first capacitor sufficiently to cut off said first and second switching transistors for a time interval greater than that required for the central office A-pulsing relay contacts to open during charging of said first capacitor.

Claim 9

Dependent Claim 272 words

A two-port network for disconnecting a local subscriber battery charging circuit fRom a cable pair and a central office talking battery for a prescribed time interval after initiation of a dial pulse by a telephone of a physical circuit, comprising first and second switching transistors having emitter electrodes connected to different terminals of the output port, having collector electrodes connected to different terminals of the input port, and having base electrodes, first and second resistors, a first capacitor, first connecting means connecting said first resistor, first capacitor, and second resistor in series across the input port and connecting the respective junctions of said first capacitor with said first and second resistors to the base electrodes of said first and second switching transistors, respectively, a third transistor having collector and emitter electrodes connected to opposite terminals of said first capacitor and having a base electrode, a second capacitor, second connecting means connecting said second capacitor between one terminal of the input port and said third transistor base electrode, and third means connected across the base-emitter junction of said third transistor for discharging said second capacitor, said first and second switching transistors conducting to pass a charging current from the talking battery prior to the physical circuit telephone producing a dial pulse, said third transistor being responsive to a transient voltage on the leading edge of a dial pulse that is impressed across said second capacitor for discharging said first capacitor sufficiently to cut off said first and second switching transistors for a time interval greater than that required for the central office A-pulsing relay contacts to open during charging of said first capacitor.

Claim 10

Dependent Claim 21 words

The network according to claim 7 wherein said second means comprises a third resistor connected in series with said second capacitor.

Claim 11

Dependent Claim 35 words

The network according to claim 8 wherein said first means comprises first and second semiconductor diodes in the connections of terminals of said first capacitor to base electrodes of said first and second transistors, respectively.

Claim 12

Dependent Claim 28 words

The network according to claim 9 including a third capacitor connected across said first and second transistor emitter electrodes which are connected to terminals of the output port.

Claim 13

Dependent Claim 61 words

The network according to claim 10 wherein said first and second transistors operate in the linear region during conduction and including fourth and fifth capacitors connected across the respective base-emitter junctions of said first and second switching transistors for causing the latter to present inductive impedances during conduction thereof which cooperate with said third capacitor to operate as a low-pass filter.

Claim 14

Dependent Claim 15 words

The network according to claim 11 wherein said third means comprises a third semiconductor diode.

Claim 15

Dependent Claim 14 words

The network according to claim 11 wherein said third means comprises a fourth resistor.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1976-12-17	1977-06-18	1977-12-18	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1980-12-17	1981-06-18	1981-12-18	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1984-12-17	1985-06-18	1985-12-18	$7700.00	Window Closed / Lapsed

Automatic disconnect circuit for reducing dial pulse distortion caused by subscriber carrier equipment

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag