This circuit converts a high voltage into a frequency using an optical coupler. The transistor can be 2N2646 and the coupler admits equivalent. The circuit is from a 1974 publication.
This circuit generates 50, 100 and 200 Hz signals from a 2.2768 MHz TV crystal. The circuit can be...
This small power amplifier makes use of an output transformer given its design time. In fact, the...
This resistance meter with the CA3130 was found in an English publication from 1977. The circuit has...