Digital recorder ISD1016 (CB7963E)

Found in a Popular Electronics from the 90s, this digital recording circuit uses an unusual integrated circuit today.

Common Gate FET Stage (CB4685E)
This field effect transistor amplifier circuit in common gate or common port configuration is from an old...
PH meter (CB20731E)
This circuit was obtained in an old American documentation. The integrated circuit used is...
LM393 Zero Crossing Detector (CB4484E)
This zero crossing detector is of the 1993 Motorola Linear Interface ICs. The source is...