US3601560A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device for busying a telephone switch
Assignee: CMC TELECOM Corp
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Filing: 1969-08-14
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Granted: 1971-08-24
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Expires: 1989-08-14
Abstract
Abstract A completely automatic and self-powered device provided with solid-state components allowing high input impedance on busy circuits obviating interference with dial pulses or audio during conversation on a telephone line, having a built-in time-delay and steering circuit to allow proper switch train release regardless which party on the line hangs up first, with indication of a completed operation by means of a low current lamp and internal divider, once operated, providing a ground to the telephone switch (usually a Strowger switch) to busy it out to all accessing switches until removed, and providing automatic resets when removed from the telephone jack.
Inventors
- 👤 Jim C Garrett
- 👤 Robert H Johnson
- 👤 Jack Shelton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 06:56
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/08; H04M3/12
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
180 words
A device for automatically busying a telephone switch in a telephone circuit that is in use so that said circuit will be bypassed by incoming calls after the same is no longer in use, comprising: a plug comprising ring, tip, sleeve and ground jacks adapted for connection to the corresponding terminals of said switch, said sleeve jack being grounded when said telephone circuit is in use, a switching circuit between the sleeve and the tip jacks and including two sets of switch contacts of a relay, a transistor in said switching circuit held ''''off'''' by a reverse bias voltage between the tip and sleeve jacks, and a steering diode to conduct current from the ring to the tip jacks to allow the transistor to be biased ''''on'''' when the two sets of relay-switch contacts are in normal closed position connecting the switching and a time-delay circuit, said time-delay circuit including a thermistor and the coil of said relay in circuit with one of said switch contacts to control operating current to said coil according to the resistance of said thermister.
Claim 2
Independent Claim
180 words
A device for automatically busying a telephone switch in a telephone circuit that is in use so that said circuit will be bypassed by incoming calls after the same is no longer in use, comprising: a plug comprising ring, tip, sleeve and ground jacks adapted for connection to the corresponding terminals of said switch, said sleeve jack being grounded when said telephone circuit is in use, a switching circuit between the sleeve and the tip jacks and including two sets of switch contacts of a relay, a transistor in said switching circuit held ''''off'''' by a reverse bias voltage between the tip and sleeve jacks, and a steering diode to conduct current from the ring to the tip jacks to allow the transistor to be biased ''''on'''' when the two sets of relay-switch contacts are in normal closed position connecting the switching and a time-delay circuit, said time-delay circuit including a thermistor and the coil of said relay in circuit with one of said switch contacts to control operating current to said coil according to the resistance of said thermister.
Claim 3
Dependent Claim
50 words
A device according to claim 1 including: an indicator lamp in circuit with the transistor and the one of said relay switch contacts, and a voltage divider to provide line-operating current sufficient to light said lamp while reducing current flow in said line to render the ''''A'''' relay thereof inoperative.
Claim 4
Dependent Claim
45 words
A device according to claim 2 in which a ground is maintained on the sleeve jack during normal use of the telephone circuit by parties at both ends thereof, the steering diode holding the path between the ring and tip jack open during such use.
Claim 5
Dependent Claim
31 words
A device according to claim 3 in which, when one party hangs up, polarity of the telephone circuit is restored to normal and the ground on the sleeve jack is retained.
Claim 6
Dependent Claim
34 words
A device according to claim 4 in which, when the other party hangs up, the steering diode acts to remove the ground from the sleeve jack, and the switching circuit turns the transistor ''''on''''.
References Cited (Backward Citations)
US3247325A
Cited
US3430000A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-08-23 | 1975-02-22 | 1975-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-23 | 1979-02-22 | 1979-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-23 | 1983-02-22 | 1983-08-24 | $7700.00 | Window Closed / Lapsed |