| 摘要 |
In a smoke detector with a pulsating radiation source (1), a radiation receiver (16), which is activated by scattered radiation in the presence of smoke in the radiation range, is disposed outside the direct radiation range of the radiation source (1). The smoke detector has an evaluation circuit which emits an alarm signal if the output signal of the radiation receiver (16) exceeds a predefined threshold value. A reference cell (12), with which the light scattered onto the radiation receiver (16) in the presence of smoke can be monitored, is disposed in the direct radiation path of the radiation source (1) near to the radiation receiver (16). The signal of the reference cell can be used directly to activate an interference signal as soon as it falls below a specific threshold value or the flow of the radiation source (1) can be controlled with it in such a way that the radiation scattered by the smoke and received by the radiation receiver (16) is independent of the contamination and ageing of the radiation source. In the latter case, an interference signal can be activated as soon as the flow of the transmitter exceeds a specific threshold value. <IMAGE> |
