I have a DSL modem that periodically stops modeming. I've upgraded the firmware to the latest rev(s), double-checked power connections, and prayed, but to no avail. A power cycle solves the problem, but eventually it fails again. There doesn't seem to be a pattern to the failure, either; hot weather, cold weather, it dies.
It would be nice to be able to powercycle the DSL modem when it failed. X-10 was the first obvious choice, but my previous experiences with the "bottlerocket" stuff showed that it was't all that reliable. Besides, it wasn't much as trying to do it yourself..
I wanted to learn how to drive things from the parallel port. So I first figured out how to turn an LED on and off.
Next: drive a relay. I would have liked to have taken power from the parallel port, but it was not reccomended. Used an external 9v battery to open & close it.
Interface to the parallel port: had some DB9 <-> DB25 cables with RJ11 in between. Found a DB-9 female connector for the controller side.
Finally, the hookup: two female power plugs, and a male <-> male connector. Relay between the power plugs. Power source on one side, and male-male cable to the modem on the other.
Then: what to put it in? Found an 8mm tape case.