This old fashioned transistor amplifier was found in a publication of the year 1958. Transformer are the critical components in the circuit and power comes from 6 D cells.
We found this circuit in an English magazine from 1976. The magazine no longer exists, but just...
I found this simple zener diodes voltage divider circuit in an old documentation. The resistor...
This circuit locks after a short touch on the sensor. The circuit can be powered by voltages from 5...