This circuit is from a 60's documentation. The capacitance C1 can be between 20 pF and 0.01 uF depending on the generated frequency. Equivalent transistors may be employed.
The components used in this 80's circuit are not common today. The circuit is very sensitive and must...
This flood or humidity alarm was found in an English publication in 1991. It can still be fitted...
We found this circuit in an old amateur radio manual. The circuit makes use of PIN diodes to...