This optically coupled circuit was found in the February 1968 Radio Electronics magazine. The circuit uses an LDR in modulation. Transistors are types of the time.
The circuit shown in the figure activates a small indicator lamp that will start to flash when the...
The circuit shown is from National Semiconductor's Linear Applications Handbook. The LM3900 is a...
This circuit was found in a 1976 documentation. It can be used with old tape recording mechanisms for...