R1 may be 10k and R2 100k. The transistor can be the BC548 and instead of the small lamp we can use a series LED with a 1k resistor. D1 is germanium and C1 is 10 nF. C2 can be 47 nF.
Suitable for alarm applications, this circuit is a modification of the previous one. We found it...
We found this circuit in a French technical documentation from 1982. The circuit can be...
This circuit is called by radio amateurs Roger Beep, which is the beep that is heard when the...