On Wed, 18 Sep 2019, Jon Elson via cctalk wrote:
Oh, my Gosh! the first 3 pics are of a KTU phone
system. If you are OLD enough, remember the phones with
5 line select buttons and a red hold button below the
rotary dial? That is what that unit supports, the 565
phone.
Please don't let anybody call the 25 pair 50-pin miniature
ribbon connector (RJ21), "Centronics"!