With this circuit found in an American documentation from 1969 it is possible to vary the selectivity (Q factor) of a tuned circuit. The operational is from that time.
Found in documentation from the 1980s, this amplifier uses an integrated circuit from the time....
This is a one-channel application for the Texas Instruments TMP390 sensor obtained directly from...
This moisture-activated relay was obtained from an American documentation from the 1980s,...