The JEM24 Expansion Module is used by end-users who need additional feature/line buttons and do not want to see them by scrolling on the main screen
Further, in the J100 Series is the J179 IP Phone. It is the premium workhorse model which addresses the need for everyday voice communications.
The J169 IP Phone is the workhorse model which addresses the need for everyday voice communications. It is designed for knowledge workers that need the full range of UC features to do their job.
The Avaya J139 IP Phone is a cost effective, entry level IP Phone that addresses the need for secure, basic voice communications for users within large Enterprises and Small and Medium sized companies. It is well suited for users that make a low number of calls on a daily basis and need a minimal feature set.
The first model in the J100 Series is the J129 IP Phone which has been shipping since December 2016. The J129 is the lowest-priced model in the family.