Does anyone know what the serial protocol type for the following controllers service tools? Part of me thinks these are 485 but I don't want to find out the hard way...

DMC-I
300A
MPH1
MPH2

Dmc I believe is a type of 485 but I think it's modified, ie there's 24v power on some of the pins. Do you not have a laptop to connect to these? You can get the orange adapter cable for dmcs from vertical express.

If you are trying to do something else get a 2 channel scope and you can see what protocol its using by comparing the waveforms against known protocols. If you are please do tell. The days of folks doing that sort of stuff to that age of equipment I thought was behind us. Most folks hear mph or 300a and the only thing they want to do is rip it out and replace it. Im in that camp too honestly. DMCs are good though...

I do have a laptop but not the correct cable. I can get away with a 25 pin to 9 pin with 232 null modem on Tac 20/32, but wasn't sure if they did some funky stuff to force you to purchase the proper orange cable.

I do have a scope, I did not think of verifying with that method but could be worth a shot. I'll gladly tell if I get around to it.

I hear ya, its definitely the easier option to get a fresh set of modern problems!

DMC is 485 but not standard. You need a 232 to 485 converter and it will not work with any kind of USB serial adapter. It needs a native serial port with the correct ACPI driver. The 3 Schindler controllers are all the same and use the same HHT program. They’re straight 232 like a Tac20. Use a 9 to 25 pin cable or adapter. NO NULL MODEM.

Appreciate the post! My mistake when I mentioned null modem, I just use my usb to serial and unsure why I type that. Cheers!