Found in documentation from the 1990s, this circuit drives an SCR with a delay that depends on C1 and can be set to R1. The load depends on the SCR.
The circuit shown was found in the National Semiconductor's Linear Applications Handbook of 1994....
This circuit from a Popular Electronics shows how to take the audio signal from a telephone line...
This circuit is from a Radio Electronics from April 1972. The circuit uses power transistors of...