We found this code key or coded keyboard in a publication from the 90s. The circuit uses components that are still common today and is powered by a 12 V voltage according to the relay used.
We find this circuit in an 80's EDN. The circuit can be used with equivalent operational,...
This full-wave circuit was obtained in Motorola's 1974 unijunction transistors manual. The circuit...
This circuit was found in Motorola documentation from 1966. The lamps are according to power and...