Intercom (CB21660E)

This good gain circuit was found in a Popular Electronics from April 1967. The transistors are germanium of the time.

Low Consumption Pulsator (CB20346E)
This circuit produces the ticking of a clock on a common piezoelectric transducer. The circuit has an...
Band Pass Filter 741 (CB16220E)
The basis of this circuit is a double T in the feedback, which has the components calculated to...
Phototransistor Optical Ttrigger (CB14648E)
This configuration was found in the Texas Instruments optoelectronics manual. PNP transistors...