This circuit with germanium transistors is from 1960 and was found in Mullard's transistor application manual from 1960. The circuit can be adapted to use more modern transistors.
This symmetrical or dual source without regulation is indicated for the feeding of experimental projects...
We can say that this circuit is equivalent to a unijunction transistor in the relaxation...
The passage of an object in front of the LDR, producing a shadow or even turning off the ambient...