Definity Phone system, it is a great system to be used as a small business phone system but can grow extremely large. The Definity System is a digital phone system which can enable up to hundreds of phones, caller ID, voicemail, and many other features. Like many other Legacy Phone Systems, this classic is no longer being supported directly by Avaya. If your business is still running on a Lucent/Avaya Definity phone system and you are having difficulty finding anyone that can provide you with help or support, give us a call at Merlin and let us make things right!