Using a 4046 PLL this circuit was obtained from the October 1994 issue of Electronics Now magazine. The circuit can be modified to generate signals at other frequencies.
This circuit was found in a General Electric documentation from 1966. It uses discrete components...
The CMOS TLC555 [equivalent to the bipolar 555] can be used as a monostable in the configuration...
This small audio amplifier was found in an American publication in 1975, The integrated circuit used...