This circuit is from the 1983 Intersil Databook. The circuit has an A / D converter for display of 4 and a half digits being powered by a voltage of 9 V.
This circuit of a voice-controlled switch, Vox or sonic switch was obtained in a Popular...
I found this circuit in a 1992 Electronics Experimenter Handbook. The circuit can be easily...
This is the circuit of a commercial amplifier sold in Japan in the 1960s. The circuit for hearing aid...