This circuit uses a resonant reed switch at the trigger frequency. The circuit is from General Electric in a 1966 documentation. This type of component is rare today.
This is the basic configuration of an operational amplifier sample & hold circuit. The FET and...
The integrated circuit 4136 consists of operational amplifiers of type 741 in the same enclosure and...
We find this circuit in a 1987 publication. It makes use of comparators constructed around the 741...