Serial switch with PIN diode (CB21257E)

This circuit was found in a Popular Electronics from the 90's. The circuit is connected in series.

Analog multiplier (CB7392E)
Suggested by Fairchild in a 1980s publication, this multiplier uses operational amplifiers from that...
Touch Switch (4) CB12189E (CB12189E)
We found this circuit in an English publication from 1980. It provides a logical output signal when...
5W amplifier (CB17330E)
This unusual amplifier configuration is from 1986. The circuit has a high resting current given the...