This circuit was found in a Popular Electronics from the 90s. The power source must be symmetrical and the operational amplifiers can be 741.
With the coded activation of the relays, it is possible to control which of the 16 outputs...
The integrated circuit used in this application is not very common. Transistors and resistors...
This simple circuit makes use of neon lamps to indicate the voltage of a power grid. The lamps are...