Created page with "The Tektronix 4551 is a light pen system. * [http://w140.com/tek_4551_1971_cat.pdf Tektronix 4551 Description in 1971 Catalog (PDF)]"
(Created page with "The Tektronix 4551 is a light pen system. * [http://w140.com/tek_4551_1971_cat.pdf Tektronix 4551 Description in 1971 Catalog (PDF)]")