This circuit was obtained from a Philips documentation from 1968. The transistors can be replaced with equivalents, only with care so that the doubles are exchanged for matched pairs.
This circuit is from an old American documentation using LEDs in the rectification. The circuit...
General Electric suggests this circuit in an 80's documentation. The circuit makes use of PUTs...
This circuit was found in an 80's Electronic Engineering. The circuit uses a multivibrator with...