In use telephone indicator (CB8665E)

This circuit was found in a 90s Electronics Now. The circuit can use a TIC106 for the SCR.

10-minute timer (CB20361E)
We found this conventional circuit with the 555 in a documentation from the 70s. Several similar or...
1 kHz Tuned Filter 741 (CB19118E)
The gain of this circuit at 1 kHz [and 40 dB falling rapidly when the frequency deviates from this...
SCR Dimmer (CB14822E)
This traditional dimmer configuration for incandescent lamps and heating elements was found in an...