The AT&T Partner MLS phones were the original Partner phones. They range from smaller four line phones with no speakerphone like the MLS-6 phone, to the MLS-34D phone which has a display and is a two way speakerphone. The displays on the MLS phones will show caller ID if you have a Partner II system with 206EC cards or a Partner ACS system. Otherwise, the lcd displays on the MLS phones will just show time, date, and last number dialed.