The frequency of this circuit can be varied from zero. The circuit uses the CMOS 4046 and was found in the November 1984 issue of Radio Electronics magazine. The base frequency is given by C1.
In the figure we have the way to use a low-cost digital clock chip to trigger an alarm. The...
This circuit is the traditional 555 oscillator that produces a hum in the piezoelectric...
This circuit was found in a computer publication from the 1970s. The transistors can be the BD135...