US3969591A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuit for preventing impulse generation by operating a hook switch in a telephone set
Assignee: Iwasaki Tsushinki KK
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Filing: 1974-12-18
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Granted: 1976-07-13
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Expires: 1994-12-18
Abstract
Abstract A circuit for preventing impulse generation caused by operating a hook switch in a telephone set, in which the hook switch has a make contact and a break contact which are make-before-break contacts in going to the OFF-hook condition, and are break-after-make contacts in going to the ON-hook condition. A capacitor is charged through the make contact when it is closed in the OFF-hook condition. A transistor switching circuit is provided to turn ON by the charge on the capacitor so as to short-circuit between telephone line terminals of the telephone set when the break contact is closed in the ON-hook condition.
Inventors
- 👤 Kouichi Sekiguchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:23
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/66; H04M1/667; H04M1/67
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
130 words
In a telephone set, a circuit for preventing impulse generation by the operation of a telephone hook switch, comprising: the hook switch having a make contact and a break contact which are make-before-break contacts when going to the OFF-hook condition, and break-after-make contacts when going to the ON-hook condition; a capacitor connected to said make contact to be charged through said make contact when said make contact is closed in the OFF-hook condition, and to be discharged through said break contact when said break contact is closed in the ON-hook condition; and a transistor switching circuit connected to said break contact and said capacitor and turned ON by the charge on the capacitor to develop short-circuit between telephone line terminals of the telephone set when the break contact is closed.
Claim 2
Dependent Claim
130 words
In a telephone set, a circuit for preventing impulse generation by the operation of a telephone hook switch, comprising: the hook switch having a make contact and a break contact which are make-before-break contacts when going to the OFF-hook condition, and break-after-make contacts when going to the ON-hook condition; a capacitor connected to said make contact to be charged through said make contact when said make contact is closed in the OFF-hook condition, and to be discharged through said break contact when said break contact is closed in the ON-hook condition; and a transistor switching circuit connected to said break contact and said capacitor and turned ON by the charge on the capacitor to develop short-circuit between telephone line terminals of the telephone set when the break contact is closed.
Claim 3
Dependent Claim
51 words
In a telephone set having a circuit for preventing impulse generation according to claim 1, said circuit including a first diode provided between said capacitor and said make contact, and a series connection of second diodes connected in parallel with the series connection of said first diode and of said capacitor.
Claim 4
Dependent Claim
91 words
In a telephone set having a circuit for preventing impulse generation according to claim 1, in which said transistor switching circuit comprises a first transistor having an emitter-collector path connected across said telephone line terminals through a diode bridge, a second transistor having an emitter-collector path connected across the base-emitter path of said first transistor through a third diode, and a fourth diode connected between the base of said second transistor and said capacitor, said break contact being connected across the base-emitter path of said second transistor through said fourth diode.
References Cited (Backward Citations)
US3471650A
Cited
US3525819A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-07-13 | 1980-01-12 | 1980-07-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-07-13 | 1984-01-12 | 1984-07-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-07-13 | 1988-01-12 | 1988-07-13 | $7700.00 | Window Closed / Lapsed |