Adjustable reference (CB21540E)

We found this circuit with 5.3V zener in a Philips publication from the 60s. The op amp could be a modern equivalent.

Light Sensitive Oscillator with the 555 (CB13794E)
This circuit provides a signal of higher frequency the greater the intensity of the light incident on...
Rectangular Generator LM3909N (CB4558E)
This circuit was obtained from a 1978 Practical Wireless. It generates a low frequency, low...
Locked relay (CB21220E)
This circuit can be used as a lockable shield. A pulse activates the relay that remains on even...