The circuit below was suggested by the Motorola Linear Databook of 1990. The component used is uncommon and the power can be between 7.5 and 12 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...