For the 1 MHz frequency, the pass band of this filter is only 120 Hz wide. The filter is suitable for telecom applications and its impedance is 600 ohms.
With this circuit it is possible to use a common hair dryer as a hand dryer. The circuit is timed...
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...
This circuit was obtained in a 1975 magazine, but it can be easily assembled using BC548...