Continuous power is not only great sounding voice and the voice is not as easy to cause intermittent attention, so it is mostly dirt alert tone or intermittent. The device can be used with any 12V power supply for continuous alarm equipment, making intermittent working condition. It can also be used to control any 12V powered lights, so that intermittent flashing.
The device schematic is shown below. In fact, the working principle of this device and the circuit structure and the Figure 7 circuit is the same, but also the two with the 4011 non-IC for ultra-low frequency oscillator gate, the other two gates in parallel with the non-shaping up as a buffer level; the 2N2222 transistor for output amplification, and its collector accused of siren or the lamp current control. If the accused is greater than the current siren 1A, 2N2222’s collector current is small, the driver can not, it would have to take a breaker to drive to the circuit breaker contacts connected in series in the power circuit of the controlled object. Intermittent intermittent time depends on the graph product of R1 and C1, values shown in the diagram, the interval time is about 3 seconds. Do not use electrolytic capacitors C1, the paper dielectric, polyester films are available, if the moment at hand is not so high-capacity capacitor can be easily purchased on the five to 0.1µF capacitor in parallel.
To change the interval time, you can change the value C1 or R1, the heavier intermittent long time; number of small, intermittent time is short.
In parallel with the circuit breaker or the guard diode is a diode, 2N2222 tube to protect against the inductive loads generated by the reverse high voltage breakdown. If charged with a resistive load, such as light bulbs, this diode can not answer. The diode voltage can be more than 50V, current is greater than any rectifier diode 1A.