Found in American documentation from the 1980s, this circuit prolongs the ringing of a doorbell or chime powered by a 6 V continuous voltage. The transistor can be a BD136.
In the figure we have the amplifier application in a NOR gate, with reference voltage equal to the...
Found in 1965 Radio Shack documentation, this circuit has a crystal phone output in the 14.8 kHz...
This oscillator or clock generator generates rectangular signals and frequencies up to 100 kHz....