This traditional TTL configuration was obtained in a 1977 documentation. The supply must be made with 5 V and the capacitors can be changed for operation at other frequencies.
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...