Model F keyboard

The Model F was a series of computer keyboards produced mainly from 1981–1985 and in reduced volume until 1994 by IBM and later Lexmark.^[1] Its mechanical-key design consisted of a buckling spring over a capacitive PCB, similar to the later Model M keyboard that used a membrane in place of the PCB.

The Model F first appeared with the IBM System/23 Datamaster all-in-one computer. It is best known as part of the IBM Personal Computer in 1981 with some keycap label differences, and its subsequent release with the IBM Personal Computer/AT, where it was reconfigured with the AT protocol and some layout revisions.^[2][3] After the introduction of the Model M keyboard, production was ramped down and eventually limited to replacement units for existing installations.

The capacitive design is widely considered superior to that of the later membrane design used on the Model M.^[4] It has a lighter actuation force of about 600 mN, a crisper feel, and louder feedback. It also has a higher MTBF of over 100 million keypresses, and full n-key rollover. These advantages were sacrificed in the Model M in order to lower manufacturing costs.

IBM Model F (1984)

The sound of an IBM Model F from 1984.

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