universal warning alarm

7-28 elektor july/august 1980 37 1 universal warning alarm 3 ... 15 V 5 ... 20 mA v!rs. 0 61 ip Mc T R511 pH i1 used to pulse a second oscillator (N5 and N6), which is set at an audio frequency. The mark space ratio of the first oscillator can be varied by means of P1 and P2. It can then be seen that P1 determines the length of time that the second oscillator is enabled. Conversely, P2 determines the time that the second oscillator is disabled. The frequency of the second oscillator can be varied by means of P3 over the range of 40 Hz ... 15 kHz. The output of the circuit will be a pulsed tone of the frequency deter- mined by P3, the "on" time deter- mined by P1, and the "off" time IC1 IC2 IC3 1â– 1W C2 * see text A device to attract one"s attention when a certain condition is not being fulfilled would have a wide range of applications. The circuit presented here is versatile enough to provide an alarm for any application whether requiring immediate attention, or just reminding on...