| 摘要 |
In response to oscillator output pulses, a sample pulse generator supplies sample pulses to a fire sensor. In response to the sample pulses, the fire sensor produces a fire sensor signal. A judging circuit receives the fire sensor signals and, if they exceed a predetermined level, produces a judging pulse having a longer pulse duration than the oscillator pulses. This judging pulse is used to trigger an alarm signal. A monitor circuit consists of an AND gate and an OR gate. The AND gate receives as inputs the oscillator pulses and the judging pulses. The OR gate receives as inputs the output of the AND gate and the sample pulses. The output of the OR gate constitutes a monitor pulse that allows the simultaneous monitoring of three conditions, as follows: (1) Lack of a monitor pulse indicates equipment failure. (2) A monitor pulse with the same waveform as the sample pulse indicates normal operation (i.e., the oscillator and sample pulse generator are working but no judging pulse is being produced-no fire is detected). (3) A monitor pulse with the same waveform as the oscillator output pulses indicates a fire has been detected (i.e., a judging pulse is present and the oscillator is functioning).
|
