Modulated light receiver (CB21790E)

We found this circuit in a Mullard manual from 1960. The transistor is a phototransistor of the time. The gain is 3 dB.

DC-AC converter (CB12410E)
Published in 1988 in Hands-On Electronics, this circuit converts the 12 V of a battery into 120 V...
Transistor microammeter (CB22302E)
This 10 mA microammeter circuit can measure currents of 50 uA. The circuit is from a publication from the...
Sophisticated Regenerative Receiver (CB25691E)
This receiver was found in an article in Electronics Now magazine in March 1994. The coils are...