We found this circuit in a documentation for radio amateurs from the 70s. The transistors can be the BC548. With it, small speakers of 4 or 8 ohms can be used as microphones.
I found this circuit in an English publication from 1989. This configuration can be mounted with...
This circuit can be used to amplify signals up to 150MHz. The JFET can be MPF102 or BF245 and the...
In this circuit of 1987 the player has to briefly press one of the keys trying to hit which LED...