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.

Zener Regulated Wien Oscillator (CB14907E)
This sinusoidal oscillator was found in Radio Electronics in 1989. It uses a 741, but other...
Flash with virbrator (CB23725E)
This is the circuit of a commercial flash from the 60’s. The circuit was published by the march...
5V Powwr Supply Crowbar protection MC3425 (CB14530E)
This circuit is suggested by Motorola in its 1990 Linear Databook. The integrated circuit is no...