If you’ve got a serial CPS cable, you can also use the DTR SMS Tool. It kind of looks like an e-mail client, except that it’s for sending and receiving arbitrary messages with the DTRs.
I’m a computer engineering nerd, so what fascinates me is that when you connect to a DTR with SMS Tool, the DTR’s display changes to read “MODEM SESSION.” I’m trying to find an inexpensive tool that will let me watch the serial data between the PC and DTR when messages are being sent and received. If I could figure out the protocol, it wouldn’t be hard to program a PC or a simple microcontroller board to send automated messages to a DTR talkgroup - security alerts, telemetry, whatever you can think of.
Just in case anyone reading this has some knowledge in the area of using a DTR for data communication: I’d love to hear from you.