so you're asking if the other pins are passed through (besides 1&2)
On the express, all the pins on DMX IN are passed to DMX OUT. The connectors are wired in parallel.
All I have done is taken one of the window alarms you get at Lowes and de-solder the magnet switch and solered in 2 wires and they will create a "loop". then made a jumper for the last controller. with all the com. lines plugged in no alarm sound, as soon as a wire is removed I have sound. I also have tied it in to my alarm system for my house and they will call me.