One option might be to search the web for "nand gate using relays". That will give you the answer, which might be a little spoilery, but you can try to puzzle

One option might be to search the web for "nand gate using relays". That will give you the answer, which might be a little spoilery, but you can try to puzzle out how it works from the solution. I found this[0], which is nice in that it's interactive (you can click the inputs to change their values and see how the current flows), though I think the visuals are a little harder to understand. Would be nicer if it had clearer delineation of the relays, and their inputs and outputs labeled with more than just their voltages. [0] https://everycircuit.com/circuit/4954026060021760/relay-based-nand-gate https://everycircuit.com/circuit/4954026060021760/relay-base...