You can still use the TD1 modules and the cables. TD1 modules are some LEDs and some resistors - not more and not less. At Datavideo-Homepage you can find a circuit diagram for testing the modules (exactly for the actual model TD-3, which is compatible). Replace the switches with a relay output. The relais an be controlled by an Arduino, which read the ATEM state like a BM tally box, but also with green ligtht
. Hey, you work at a high school. So you will find some guys, who can dot it as a DIY project. The material costs round about 100,- € (Arduino, Ethernet shield, 2 8-channel relais shields or one 16 channel relais shield, a box and some connectors and cables).The program code can be found on internet (or write me a PM - my ATEM-Datavideo-ITC100 adapter does exactly the same).
I‘m not sure, but maybe you can look to my post at german BM user group on facebook.
https://www.facebook.com/groups/BMD.GERMAN.ATEM.USERSEdit: I also found an old manual with a TD1circuit at 5V. Im pretty sure, some resistors and transistors could do the same work as the relais and are much smaller and quiet....
Edit 2: I made a test. My TD-3 runs with approx 20 mA. So it is near to maximum power at Arduino output-pins. Maybe it is enough power, maybe an amplification would be necessary. I also don‘t know the maximum distance with 5V. I also tried a ULN 2803, but it switches to ground, but TD-unit has common ground....A circuit switching to +5V (or what ever) is needed. Sorry, my knowlege with electronic is basic, but there wil be a cheep and small solution.
Edit 3: with short cables, my TD-3 run directly with the Arduino. I set the resistors on a value, the TD-3 takes 15mA.