| 摘要 |
A smoke detector comprising a smoke detection cell of the ionization type and an electrical network providing for a.c. operation of the detection cell. The impedance of the detection cell changes in the presence of airborne combustion products and alters the operating frequency of the network. The frequency change is sensed to actuate an alarm. A.C. operation avoids the problem of d.c. instability in the high impedance detection cell circuit and simplifies sensing the electrical condition of the detection cell. The electrical network typically uses MOS-FET devices as the active circuit elements.
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