Hi ggarza. RS-232 is not designed for more than two devices to communicate. It might be possible with enough
diodes and careful programming, but I expect it would be a challenge.
A better approach might be to use RS-485, which is designed to support more than two devices.
RS-485 information.
There are RS-485 to RS-232 converters available that will let you connect your other device; the -2220 controllers
have an RS-485 port already.
Matt