Hughes suggests this circuit in a 1968 documentation. The circuit uses old transistors that can be replaced with equivalents. MOSFET is the critical component of the circuit.
With two cascading tunnel diodes, this circuit found in a 196 General Electric documentation...
Found in General Electric's 1969 documentation, this circuit uses two Foto Darlingtons to control...
This circuit is used in the analog part of the telephone lines. The same circuit can directly...