| 摘要 |
1. A fire alarm having a radiation source (5 ; 25, L2 ) operated in a pulsed mode, the radiation source transmitting electromagnetic radiation to a measuring chamber (1) which is accessible to air to be examined for the presence of smoke and aerosol particles and having a receiver being connected with an evaluation unit (S) which delivers an alarm signal as soon as the signal delivered from the receiver exceeds a predetermined threshold, characterized in that the receiver is an acoustical receiver (7 ; 17, L4 , 27) for taking-up air vibrations produced by the absorption of radiation pulses by the particles. |
