This circuit uses a General Electric coupler from the time of the publication in the 1980s. Equivalent SCR can be used.
This circuit came out in a Popular Electronics from December 1995. It is a double T configuration that...
Found in a 1967 Electronic Design, this circuit can detect pulses as narrow as 0.2 us. Active...
This is the basic configuration of a Colpitts LC oscillator using a CMOS gate. ...