The company I work for is new to the alarm game- we always used to sub it out, but then the company we subbed it to decided to try and get into the AV/Automation game as well and so we have moved it in-house. I'm working on a design and proposal, and the experienced alarm guy we hired is on vacation, so I'm asking here.

I have a standard alarm system in the main house- now the homeowner has decided to build a detached "garage" structure that he also wants to have on the same system. The detached structure is a few hundred feet away, and the contractor laid 1.5" conduit between the main house and the garage, so I am trying to limit the amount of cables I have to pull, as I also have network and audio/video needs in the detached building.

My question is: can I simply put a zone expander (it's a DSC system) in the detached garage to allow for the additional devices (one keypad, 4 doors, 1 motion/GB), and run a single cat5e cable back to the main alarm panel to allow for the communication?