Found in a 90's EDN this circuit can be used as a shield. The transistor is a general-purpose type and the frequency of the emitted sound is determined by R1 / C1.
The Texas Instruments TPS7A92 integrated circuit consists of a low-voltage (LDO) linear voltage...
Found in a 1969 EDN, this high current circuit, not indicated in the documentation, uses...
This circuit was obtained in a 1991 Electronics Handbook. The publication no longer exists, but...