| 摘要 |
<p>The amount of noxious gas or vapour such as oxides of carbon or hydrogen in the air is detected by surveillance system which provides an alarm when dangerous levels occur. A power supply unit (1) powered from mains supply (2, 3) provides regulated power for gas detector (6) which contains a heater (7) and a sensitive cell (8). Potentiometers (11, 12) permit adjustment for an amplifier (10) to set threshold at which a switching amplifier (14) is operated to drive a relay (15) with alarm indicator (9) circuit. A safety circuit (27) and ventilation control circuit (24) ensure that the amount of noxious gas is reduced in the air.</p> |
