Patent US2728644A successfully refreshed from Google Patents.
Patent US3383513A successfully refreshed from Google Patents.
US3383513A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electric key-card system with a plural photoelectric cell bridge circuit
Assignee: Individual
•
Filing: 1965-03-22
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Granted: 1968-05-14
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Expires: 1985-03-22
Abstract
No abstract record available.
Inventors
- 👤 David W Douglas
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 14:27
CPC Classifications
G; G07; G07C; G07C9/00; G07C9/20
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
128 words
AN ELECTRONIC CIRCUIT ADAPTED TO RESPOND TO A PREDETERMINED CONDITION OF RELATIVE INTENSITY VALUES OF A PAIR OF LIGHT BEAMS, SAID CIRCUIT COMPRISING, A PAIR OF PHOTORESISTORS FOR RECEIVING CORRESPONDING ONES OF SAID LIGHT BEAMS; RESISTIVE CIRCUIT MEANS HAVING TWO OUTPUT TERMINALS AND COUPLED TO SAID PHOTO-RESISTORS TO PROVIDE AN ELECTRICAL BRIDGE CIRCUIT; MEANS FOR EXCITING SAID BRIDGE CIRCUIT WITH AN AC VOLTAGE; SUMMING MEANS COUPLED TO SAID CIRCUIT MEANS TO PRODUCE AN AC OUTPUT VOLTAGE OF SUBSTANTIALLY ZERO AMPLITUDE AT EACH OF SAID TERMINALS UPON THE OCCURRENCE OF SAID PREDETERMINED CONDITION; GATING MEANS COUPLED TO SAID OUTPUT TERMINALS AND ADAPTED TO PRODUCE AN OUTPUT SIGNAL IN RESPONSE TO A ZERO OUTPUT VOLTAGE AT EACH OF SAID TERMINALS; AND LOCK-OPENING MEANS OPERABLE IN RESPONSE TO SAID OUTPUT SIGNAL.
Claim 2
Dependent Claim
128 words
AN ELECTRONIC CIRCUIT ADAPTED TO RESPOND TO A PREDETERMINED CONDITION OF RELATIVE INTENSITY VALUES OF A PAIR OF LIGHT BEAMS, SAID CIRCUIT COMPRISING, A PAIR OF PHOTORESISTORS FOR RECEIVING CORRESPONDING ONES OF SAID LIGHT BEAMS; RESISTIVE CIRCUIT MEANS HAVING TWO OUTPUT TERMINALS AND COUPLED TO SAID PHOTO-RESISTORS TO PROVIDE AN ELECTRICAL BRIDGE CIRCUIT; MEANS FOR EXCITING SAID BRIDGE CIRCUIT WITH AN AC VOLTAGE; SUMMING MEANS COUPLED TO SAID CIRCUIT MEANS TO PRODUCE AN AC OUTPUT VOLTAGE OF SUBSTANTIALLY ZERO AMPLITUDE AT EACH OF SAID TERMINALS UPON THE OCCURRENCE OF SAID PREDETERMINED CONDITION; GATING MEANS COUPLED TO SAID OUTPUT TERMINALS AND ADAPTED TO PRODUCE AN OUTPUT SIGNAL IN RESPONSE TO A ZERO OUTPUT VOLTAGE AT EACH OF SAID TERMINALS; AND LOCK-OPENING MEANS OPERABLE IN RESPONSE TO SAID OUTPUT SIGNAL.
References Cited (Backward Citations)
US3029345A
Cited
US3221304A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1971-05-14 | 1971-11-13 | 1972-05-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1975-05-14 | 1975-11-13 | 1976-05-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1979-05-14 | 1979-11-13 | 1980-05-14 | $7700.00 | Window Closed / Lapsed |