US3912879A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Continuity and tone test set
Assignee: Individual
•
Filing: 1974-05-30
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Granted: 1975-10-14
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Expires: 1994-05-30
Abstract
Abstract An oscillating circuit which remains inactive until a connection is made between two leads causing a tone in an attached speaker. Variations in resistance between the two leads alters the audio output at the speaker.
Inventors
- 👤 William J Lawson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 19:53
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/50; G01R31/66; G01R31/67; G01R31/52; G01R31/54
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
175 words
A continuity and tone test set comprising: a housing, an opening in one side of said housing; a pair of binding posts mounted on a second side of said housing; an electrical circuit mounted within the housing and connected to the binding posts, said circuit including, a battery, a first resistor connected between the battery and the first binding post, a loud speaker connected to said first binding post through a capacitor, a first transistor having its emitter connected to the positive battery output and its collector connected to one side of said loud speaker, a second transistor, a second resistor connected between the second binding post and the base of the second transistor, means connecting the collector of said second transistor and the base of said first transistor, means connecting the negative terminal of the battery to the loud speaker, and means connecting the emitter of said second transistor to the battery-loud speaker connecting means whereby a connection between the first and second binding posts will produce an audio output at the loud speaker.
Claim 2
Dependent Claim
175 words
A continuity and tone test set comprising: a housing, an opening in one side of said housing; a pair of binding posts mounted on a second side of said housing; an electrical circuit mounted within the housing and connected to the binding posts, said circuit including, a battery, a first resistor connected between the battery and the first binding post, a loud speaker connected to said first binding post through a capacitor, a first transistor having its emitter connected to the positive battery output and its collector connected to one side of said loud speaker, a second transistor, a second resistor connected between the second binding post and the base of the second transistor, means connecting the collector of said second transistor and the base of said first transistor, means connecting the negative terminal of the battery to the loud speaker, and means connecting the emitter of said second transistor to the battery-loud speaker connecting means whereby a connection between the first and second binding posts will produce an audio output at the loud speaker.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-13 | 1979-04-14 | 1979-10-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-13 | 1983-04-14 | 1983-10-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-13 | 1987-04-14 | 1987-10-14 | $7700.00 | Window Closed / Lapsed |