| 摘要 |
1,063,049. Alarm systems. SIOC Ltd. Aug. 4, 1964 [Aug. 1, 1963], No. 31311/64. Headings G4F and G4N. [Also in Division H3] In an alarm system, an, electroluminescent panel is supplied with power from an A.C. source via a controlled rectifier. The occurrence of an abnormal condition causes transistor 24 to become conductive and the change in emitter potential is differentiated by capacitor 36 and resistor 38 to produce a pulse which switches crosscoupled transistors 40, 54 to their conducting state to supply power to transistor 60. Transistors 60 and a normally non- conducting transistor 62 form a multivibrator 18 which now starts to oscillate causing transistors .62, 74 and controlled rectifier 16 to periodically switch on and off connecting supply 14 periodically to electroluminescent panel 12, causing it to flash. An audible alarm 48 is also sounded. Opening switch 48 stops the audible alarm and switches-off transistors 40, 54 and the multivibrator 18 stops oscillating with transistor 62 held conducting by a potential fed from the emitter of transistor 24 via diode 90 and resistor 88. The electroluminescent panel 12 is thus steadily illuminated. A switch 46 is provided so that the alarm indication may cease at the termination of the abnormal condition, or may be maintained until reset. |
