Found in Electronics now from the 90s, this circuit uses a sensor from the time, which is difficult to find today. The circuit activates a sonalert-type buzzer.
This circuit converts square (rectangular) signals into triangular signals with typical 16 V...
The transistors of this circuit found in an English 1980s documentation may be the modern BC548...
In the figure we have an AND gate with the LM3900 operational transconductance amplifier. The...