| 摘要 |
PCT No. PCT/CH83/00112 Sec. 371 Date Apr. 16, 1984 Sec. 102(e) Date Apr. 16, 1984 PCT Filed Oct. 10, 1983 PCT Pub. No. WO84/02790 PCT Pub. Date Jul. 19, 1984.In a photoelectric smoke detector, a radiation source is driven intermittently by a control circuit and the radiation influenced by smoke particles, for instance scattered radiation, is picked up by a radiation receiver. The signal of the radiation receiver is transmitted to a signal processing circuit which is transmitted to a signal processing circuit which is simultaneously regulated by the control circuit. The signal processing circuit comprises a phase sensitive circuit which reverses or inverts the received signal according to the phase of the signal of the control circuit and transmits the thus modified signal to an integrating circuit. The integrating circuit controls a display circuit by means of its integrated output signal. The display circuit can, for instance, output an alarm signal when the integrated signal, i.e. the smoke intensity, exceeds a prescribed threshold value or can display the smoke intensity. In this manner, even weak smoke signals can be surely and reliably detected even when they are fully masked by noise. Such a smoke detector can be advantageously employed as an especially sensitive and interference-resistant fire alarm. |
