Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the Sonalert type with included oscillator.
Suggested by Mullard in an old documentation, this circuit is based on a common phototransistor and on...
Other series operationals such as the LM258, LM358 and LM2904 can be used on this circuit of the...
This configuration appears elsewhere on this site. This is from a 90’s Popular Electronics and is valid for...