Found in Exar documentation from the 1980s, this circuit has a 60 dB cutoff at 1800 Hz. The circuit can be adapted to operate at other frequencies.
This version of the previous circuit uses a common transistor Hartley oscillator for modulation. We found...
This simple power supply is not regulated and the output current depends on the transformer. It...
This circuit was found in a 1992 documentation. It activates a relay when light falls on a...