This circuit is from a 1976 amateur radio manual. The transistor can be the BD136 and the frequency adjustment is done in a potentiometer. The supply can be done with voltages from 6 to 15 V.
This light-controlled circuit uses a 6 V or 12 V relay depending on the supply. The transistor can be the...
This circuit was found in the March 1999 issue of Electronics Now magazine. The meter is analog and...
This preamp with a transistor for turntables with crystal capsules was found in a Japanese...