This circuit makes use of an integrated LM2907. The circuit is from an old documentation being applied to cars that still used platinum, common at the time.
This circuit is from a Radio Electronics from May 1994. In it we have the way to connect three 4017...
In the figure we present an extremely simple circuit of a voltage source regulated by a zener...
We found this circuit in a 1987 documentation. It is a multi-tester with neon lamp and LEDs...