This circuit generates a siren sound. It was found in the April 1969 Radio Electronics magazine. The output signal is to be applied to an external amplifier.
We find this circuit in a radio amateur publication of 1977. Its purpose is to measure the...
This inverter amplifier is from a 1992 publication. NPN transistors can be BC548 and PNP BC558....
I found this circuit in a 1986 English magazine. It can still be easily assembled, exchanging Q1...