This is the circuit of the commercial Japanese megaphone of the 60s model DM-218. The circuit uses a compression speaker (horn) and is powered by 4 large batteries. The output power is 2 W.
This circuit provides a pulse train of 4 MHz or at another frequency determined by the crystal during...
This circuit was obtained in the manual of the used integrated circuit. Equivalents may be used...
ST Microelectronics has, in its line of low voltage drop linear regulators, the KD1084xx (fixed) and...