Relative impedance meter (CB7487E)

Found in a 1960 Sylvania manual, this circuit can be implemented with a modern equivalent transistor like the BC558.

Dual Voltage Source (CB25158E)
This circuit was designed to power the previous circuits of the wireless sound system, but it can...
Sensitive Photo Relay CB13492E (CB13492E)
This circuit is from the documentation of Radio Shack 1975. It can be mounted with 12 V relays,...
AC Phototransistor (CIR812E)
This circuit is suggested by the Optoelectronics Sourcebook by Texas Instruments when AC signals...