These were for Terminals that AT&T made in the mid 80's.? The terminals had a built in telephone set.? There was a analog model for use with POTS lines and a digital model for use with System 75 and 85 PBX systems.? If you have no use for it, I'd add it to my collection as I have several AT&T personal terminals 510A and D's.? Another intresting feature of these sets was they were all equiupped with touch screens.