Found in an Electronic Design from the 90s, this circuit uses high voltage operationals of the time to excite a piezoelectric motor in a bridge circuit.
Found in a 90s Popular Electronics, this circuit uses two PLL tone recognizers to trigger by touch an...
This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is...
This circuit is from 1995 documentation. In the original, the source is symmetrical at 12 V, but...