Found in an Electronics Now from the 90s, this circuit uses components that are still common. The LM3900 is a transconductance operational amplifier.
Found in Radio Electronics magazine from June 1968, this circuit produces signals from 30 Hz to...
This circuit is suggested by Motorola, using a 4N26 type coupler and an MC1733 type operative. However,...
This circuit is from a PopularElectronics of June 1992. The magazine no longer exists, but the...