Using 555 integrated circuits, this alarm circuit was found in a 90s American documentation. The signal must be applied to a good audio amplifier.
This oscillator has the output sine waveforms stabilized by a MOSFET. Equivalent types can be...
We found this synchrodyne receiver for the medium or short-wave band in the Radio Electronics...
This amplifier is suggested by Sanyo, for radio and recorder applications and makes use of a...