Found in a 90s Popular Electronics, this sensor operates by infrared reflection. The components are modern, and the phototransistor can be of almost any type.
We found this amplifier for automotive use in the Philips integrated circuit manual from 1990. The...
This interesting circuit records a few seconds of audio signals, reproducing them in a small...
Settings like this can be found at various points on this site. The trigger door can be a 4093...