This is the basic configuration of an operational amplifier sample & hold circuit. The FET and transistor are commonly used. The circuit is from an 80's documentation.
This circuit from a Popular Electronics from the 90s allows you to use an old PC as a digital...
We found this circuit in Radio Electronics magazine from June 1960. The four-transistor circuit is...
This type of answering machine was common at the time this circuit was published. Using two tape...