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.
The circuit in the figure uses the four current amplifiers of the LM3900 to generate a sawtooth signal...
This circuit was found in an old Motorola documentation from the 70s, as it uses one of its...
This circuit for an optical audio link using LED or LASER was found in a 90s QST magazine. The circuit...