Found in Popular Electronics from the 90s, this circuit is based on a PLL567 and employs high-end or ultrasonic speakers depending on the frequency of oscillations.
The L293 circuit is not common today. We found this circuit in the 1982 SGS linear integrated...
We found this bridge circuit in Electronics Now magazine from September 1995. The instrument can...
We found this divider in a circuit manual from the 90s. The circuit is intended for operation with...