| 摘要 |
1,017,178. Intruder alarms. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Aug. 28, 1964 [Aug. 29, 1963], No. 34275/63. Heading G4N. [Also in Division H3] A detector for indicating the presence of an object in a path 5 comprises: a lamp 1, the energization of which is modulated by means of, for example, an oscillator 3; a receiver 8 producing an output signal in response to radiation falling on it; and a comparator 9 comparing the phase of the signal from the receiver 8 with that from the oscillator 3, to produce an output indicative of the presence of an object in the path 5. The path from the lamp 1 to the receiver 8 may include one or more mirrors 6 and lenses 4, 7. |
