Quad Device Driver
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The History of the Quad Device Driver With Audio Input Selector
The aforementioned thingy (Quad Device Driver With Audio Input Selector) began as a relay switch used to turn a stereo on and off. It was controlled by a BASIC program (Switch 2.0) on an old Epson HX-20. It would turn on and off like a programmed VCR.
Next, I wanted it to control four separate devices. So in the winter of 2000, I designed a circuit that uses a counter (4029) IC to switch four relays, which it turn switched four AC circuits. The IC is set to count up hexadecimally (it counts from 0 to 15, then back to 0), and it is pulsed by the cassette drive remote on the HX-20. It will not work with a modern computer. It runs on Switch 3.0. (You can get an HX-20 on Ebay for $25).
Later, in Dec. 2000, I added a device that electronically switches between four audio input devices connected to an Aux jack on a stereo. This was not really necessary, but it works. (Sort of)