Found in an RF Design from the 90s, this circuit is based on components from the time. It can, however, be implemented with equivalent modern components.
The circuit shown is suggested by National Semiconductor's Linear Applications Handbook. The base...
This circuit uses a pickup coil to take the signal from a telephone line without contacts. The circuit...
In this circuit, the transistors are NPN for general use and the phototransistors can be replaced by...