Actually, there were two single-line type phones designed for use with the 4A system in mind. The rotary version was the 500R/S, and the TT version was the 2500S.

Heck... I think I still have a 2500S. In green, no less, with a speakerphone set to match.

Keep the peace(es).

Bruce Lane, Owner & Head Hardware Heavy, Blue Feather Technologies.

"Salvador Dali's computer has surreal ports..."