So I've had in my mind the idea to build a TI link switch for awhile now. This switch would basically be a small box with a common cable coming out one side and two 2.5mm ports on the other side. A DPDT toggle switch would select between the two ports, which would make it easier to upload programs to the calc and then test the program, especially when the program uses the link port (a toggle of the switch is less hassle than swapping the cable to the computer for a cable to another calc, for example).

A little later I started thinking about building a link hub for CALCnet. This would consist of a box with a small number (say, 4 or so) of 2.5mm ports, so all you have to do is plug in another calculator. No splicing of cables necessary.

More recently (yesterday), I realized how neat it would be to combine these two! So I am going to build a box with one common 2.5mm cable, three 2.5mm and one 3.5mm (for headphones ) ports on side A, a 2.5mm cable on side B, and a DPDT toggle switch to select between A and B.

Here's some awexome ASCII art to illustrate this switch/hub (top view):

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To use this, plug in a calc on the common cable, the TI-graph link on cable B, and 1 or more calculators (and/or headphones) on the A ports. All of the A ports are connected to each other at all times. The switch determines whether the common cable is connected to A or to B.

This switch allows up to 4 calculators on a CALCnet (or similar) network, and because of the way the CALCnet bus works, you can actually connect more than 4 calcs by daisy-chaining hubs. Just plug in another hub into one of the 3 ports on the A side, and you can plug in more calcs on the daisy-chained hub.

I finally decided to build this box now because I was already purchasing a 2.5mm extension cable (female/male) to build an adapter cable for a camera shutter release switch, so I just bought more cables to let me build this switch. I still need to find an inexpensive box to house it, though. Anyone have good sources to buy one of those?

I think this is a superb idea! Back in the day (by which I mean a few months ago) Alberthro was planning a set of CALCnet hubs, and he had some sources for nifty cases. Take a look at his topic for some ideas:

http://www.cemetech.net/forum/viewtopic.php?t=5089

Nice activity lights! I think I will forgo activity lights in mine to avoid requiring batteries (though I understand that batteries are needed only for the activity lights themselves). Then again, I could add a power socket so you can use a wall wart for power.

For a box I was thinking about maybe using an Altoids tin. It's a nice project box, and it comes with free mints!

I actually was planning to make something similar to this earlier, but I can see you have the better idea (I never would have thought of using an Altoids tin, or status lights, or even a switch). One thing that I was planning to do was use my school's laser engraver to engrave the CALCnet insignia onto the plastic box.

Another idea that I had for a CALCnet hub was something like a Game Boy Advance cable:

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Basically, a unit to unit cable is run through a small box, where it is connected to a 2.5mm port. Basically, this creates a cable that can be attached to another cable, and infinitely daisy chained. While this requires one cable for each additional player, it could be used entirely on its own, without other parts. Also, it could be used as a standalone cable or an extension to a Graphlink or something. It could even be interfaced with this.

Oh, that is a superb idea, and would allow cables to be modified without removing their ability to function as normal unit-to-unit cables! I'm envisioning something akin to a vampire tap in the middle of the unit-to-unit cable with the socket attached. Nice thinking. Christop, thanks, and as you say, my activity lights are the only thing that requires the batteries. Altoids tin sounds like a nice choice. And finally, compynerd, if you get an engraved CALCnet insignia, I might have to work out something where I ship you a case and some compensation to get one engraved for me.