| 摘要 |
<p>Circuitry is described for decreasing the susceptibility of a fire detector to unwanted alarms in response to variations in the supply voltage powering said fire detector. The fire detector contains a fire sensor (RC and SC), a regulator (TR1, ZD1), and an alarm comparator circuit (A2, R8, P1, R9). Switching means (TR3) are connected to the comparator circuit and switching control means (ZD1, R11) are connected so as to respond to a drop, below a predetermined level, in the supply voltage. The switching control means (ZD1, R11) are connected to the switching means (TR3) so as to cause a difference between the alarm threshold voltage input and the sensor voltage input to increase in response to a drop in the supply voltage. <IMAGE></p> |
