Self-checking light curtain system and method of operation.
Abstract
Abstract A light curtain system and method of operation which detects the intrusion of objects into a protected zone. The system is characterized in having an inherent self-checking mode of operation by logic circuits which analyze data signals from both the LED light transmitters and phototransistor receiver circuits. A shutdown signal is generated if the logic circuit determines that light is not received in a selected channel at the time that the LED is strobing light exclusively for that channel. The system further provides a relatively simple and inexpensive method of selecting and amplifying the LED transmitters and PT receivers. In the circuit each PT acts as a switch which selects itself, and a single amplifier is employed for a plurality of the channels. The circuit further provides for the concatenation of groups of amplifier/PT circuits into a longer chain using a single diode.
Inventors
- 👤 David Blau
Bibliographic Details
Claims Analysis
Total Claims: 0References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-04-10 | 1998-10-10 | 1999-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-04-10 | 2002-10-10 | 2003-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-04-10 | 2006-10-10 | 2007-04-11 | $7700.00 | Window Closed / Lapsed |