With the capacitor used, this circuit provides delays of 40 to 60 seconds. Larger capacitors can be used, and the SCR supports an equivalent. The circuit is from the 1977 RC semiconductor manual.
This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit...
The operational amplifiers used in this circuit are old. The circuit is from documentation of the 70's, but...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...