The circuit shown is from the 1994 Linear Applications Handbook by National Semiconductor. Some of the components are not currently common and should be looked for equivalents.
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...