This circuit was obtained from an American 1980s documentation. The frequency depends on the crystal and the circuit may be a PNP that reaches the generated frequency.
This triac circuit was obtained from the August 1995 issue of Electronics Now magazine. The triac...
This instrument, based on a 555, measures frequencies up to 1 kHz, but its scale can be modified by...
This is a traditional circuit in which a 741 operational amplifier is used as an audio amplifier with...