Found in an English publication from the 1980s, this circuit can be built with equivalent transistors such as the BC549. The signal must be applied to an external amplifier.
Found in a magazine from the '90s, this circuit uses an integrated circuit from the era that is...
This circuit, found in documentation from the 1990s, uses a common 7-segment LED display. The...
This circuit provides precise signals of three frequencies, using CMOS technology. The integrated...