IBM 2821 Control Unit

The IBM 2821 Control Unit was used to attach card readers, card punches and line printers to the IBM System/360 and IBM System/370 families of computers. The devices attached were as follows:

• The IBM 2540 card reader and card punch;
• The IBM 1403 models 2, 3, 7 and N1 line printer; and
• The IBM 1404 model 2 line printer and card reader.

Six models of the IBM 2821 Control Unit were available, as follows:

• Model 1 attached one IBM 2540 and one IBM 1403;
• Model 2 attached one IBM 1403;
• Model 3 attached two or three IBM 1403s;
• Model 4 attached one IBM 2540 and one IBM 1404, but only on IBM System/360 models 30, 40 and 50;
• Model 5 attached one IBM 2540 and two or three IBM 1403s; and
• Model 6 attached one IBM 2540.