| 摘要 |
1511461 Doppler intruder-detector PITTWAY CORP 12 Jan 1976 [21 Jan 1975] 01008/76 Heading GIG [Also in Division G4] An intrusion detection system covering a plurality of separate zones comprises ultrasonic wave transmitting transducers for each zone, respective receivers for each zone, a master oscillator for driving all the transmitting transducers and to which all the receivers are coupled for producing individual Doppler signals indicative of moving objects in the respective zones, and indicators at a central location for selectively indicating each zone in which a moving object is located. In the Fig. 1 embodiment each zone is provided with several transmitting transducers 27 and receiving transducers 38. Receiving and signal processing circuits for two zones are contained in each of modules 21, 26. The system can be extended by adding further dual-zone modules. Master control 11 powers all the transmitting transducers and feeds a synchronizing signal to the modules for synchronous demodulation, within each module, of the receiving transducer signals. Each module, Fig. 2 (not shown) filters the demodulated signals for its two zones to extract desired Doppler frequencies and de-energizes a relay if the Doppler signal amplitude, integrated over a one second period, exceeds a threshold value. Respective alarms 42--45 are actuated by the relay de-energizations. Intrusion into any zone also actuates a general alarm 17 of audible or visual type locally, or remotely via a telephone line or other link. Provision is made for manual testing of the alarms. |
