Elk M1 and Dahua NVR

I am planning on using my outside motion detectors (NO contacts)  to trigger my new Dahua NVR (There are 8 NO inputs) and my Elk M1 zone input.  Both inputs have a ground, so I imagine they will share the same ground.   Am I looking into problems (interference, impedence) by doing so??
  

The Elk puts out a voltage on the positive side of the zone input.  The NVR probably has a similar input circuit.  You really don't want to have a single contact connected to both inputs.  Doing so could damage one or both systems.
 
The right way to do this would be to use the motion detector to trigger the Elk, and then have a rule that turns on a relay output, with the relay contacts triggering the NVR.

Thanks RAL. That was what I was suspecting. I have spare relays on my Elk so I will use them. Sure glad I chose an NVR with inputs and outputs. This combined with the Elk any combination is possible