Using the 741 this circuit can be adjusted to values between 1 Hz and 100 kHz. The power supply must be symmetrical. We found it in the Radio Electronics magazine of November 1973.
This 2000 circuit can work with one of the many infrared remote-control transmitters described in this...
This receiver for listening on the phone was found in a Japanese magazine in 1967. The circuit uses...
The circuit shown in the figure is suggested by Intersil (www.intersil.com) and makes use of the...