Found in old documentation, this circuit is tuned to pass signals below 245 Hz with a level of 0.044 dB above 500 Hz.
The sensor for this alarm is an LDR and it consists of an oscillator that goes into action when...
We found this amplifier circuit for inductive audio pickups in a documentation from the 70s. The...
This circuit is from an American documentation from 1976. The FET can be the BF245 or MPF102 and...