The Z-600 (or Z-601 with the rackmount face) are great add ons, and you can use them with any distributed audio system that has a configurable page trigger and a page input... the doorbell tones and all of that are generated in the Elan comm box and the page override input on the Russound, Niles, etc. doesn't care if it is breaking in to play the doorbell chimes from te Elan Z-600 or your voice asking the kids to come to dinner.

The real issue is whether it will be compatible with their phones.

Remember that the comm controller can only be connected to one incoming line. If they have multiple lines this may be a problem.

If the lines are awitched through a "real" phone system with a KSU, you can program one of the CO's to go directly to the line that the Elan box is connected to, and teach them to selelct that CO, then enter the tones to enact paging and door station use.

With some systems, you will have to dial the KSU tones to open the switch to get out to the correct line where the Elan box can hear the handset tones, then dial the Elan tones to enact the page mode, then talk into the handset... I only saw that on one system, and it was an old Merlin system that I hope nobody else ever has to be forced to deal with.

KSU-less multi-line systems are easier, because they can be programmed to give to a specific incloming line from a specific CO selection.

Plain old multi-line phones are the best, one line takes you to the Elan controller and the others do not, choose the correct line and your ready to go...

Have a frank discussion now about their phone usage and future plans before you specify an Elan comm controller.