[IMSAI Guy] grabbed an obsolete XOR gate and tried a classic circuit to turn it into a frequency doubler. Of course, being an old part, it won’t work at very high frequencies, but the circuit is ...

[Dr. Cockroach] figured out a way to create an inverting NOT gate from just one LED and two resistors (one being a photo-resistor). The Dr. has since built AND, NAND, OR, NOR, XOR and XNOR gates ...