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Appendix B. 3274 Device Cables
In order to assign the device cables to the correct 3274 ports, you should be aware of the
following:
• Two categories of units can attach to the 3274:
1. Category A - 3278s, 3279s, 3287s with a 3274 attachment feature, and 3289s.
2. Category B - 3277s, 3284, 3286s, 3287s with a 3271/3272 attachment feature,
and 3288s.
Category A units must attach to a 3274 Type A Terminal Adapter; Category B units
must attach to a 3274 Type B Terminal Adapter.
• The basic 3274 is capable of attaching eight Category A units. Type A Terminal
Adapters and Type B Terminal Adapters can be ordered in various combinations to
provide a n:aximum cluster of (a) 32 Category A units or (b) 32 Category A and
Category B units, of which a maximum of 16 can be Category B units on Models lA,
1B, lC, and ID. The 3274 Model SIC can have a maximum of 8 Category A units and
4 Category B units. For detailed information concerning 3274 terminal adapter feature
combinations, refer to IBM 3270 In/ormation Display System: Conjigurator,
GA27-2849.
• Depending upon the configuration of the 3274 and its attached units, a maximum of
five device cable connector panels can be installed on the 3274 (see page B-3). Each
panel used to attach Category A units contains eight ports for attachment of device
cables; each panel used to attach Category B units contains either four or eight active
ports. Therefore, on Models lA, IB, lC, and ID a maximum of 40 ports can be
present. However, only 32 of the possible 40 ports can be used.
• There are two types of 3274 device cable connector panels:
1. Black panels, labeled "A," which are used to attach device cables from units that
attach to a Type A Terminal Adapter.
2. White panels, labeled "B," which are used to attach device cables from units that
attach to a Type B Terminal Adapter.
The lowermost panel on Models lA, IB, lC, and ID (and also the second and third
lower panels, if present) are always black, labeled" A," have ports numbered 0 through
23 (AO - A23), and are used to attach only Category A units.
• On Models lA, IB, lC, and ID the fourth panel from the bottom (if present) has a
dual function. It can be used to attach either Category A units or Category B units.
This panel can be used for one or the other category of machines, but not both
categories. When this panel is used to attach Category A units, the panel is black,
labeled "A," and has ports numbered 24 through 31 (A24 - A31); when this panel is
used to attach Category B units, the. panel is white, labeled "B," and has ports
numbered 8 through 15 (B8 - BI5).
• On Models lA, IB, lC, and ID the fifth (uppermost, if present) panel is always white,
labeled "B," has ports numbered 0 through 7 (BO - B7), and is used to attach only
Category B units.
• Port AO must always be assigned to a 3278 or 3279 with a keyboard.
Appendix B. 3274 Device Cables
B-1
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