DEC LK201

The LK201 is a detachable computer keyboard introduced by Digital
Equipment Corporation of Maynard, Massachusetts in 1982. It was first
used by Digital's VT220 ANSI/ASCII terminal and was subsequently used by
the Rainbow-100, DECmate-II, and Pro-350 microcomputers and many of
Digital's computer workstations such as the VAXstation and DECstation
families. 

The keyboard layout was new at the time, adding a set of cursor and
miscellaneous keys between the main keyboard and the numeric keypad. The
cursor keys were arranged in what has now become the standard "Inverted
T" arrangement seen on essentially all contemporary full-sized computer
keyboards.[1][2] The keyboard also added a Compose key to allow typing
of all of the characters in the terminal's extended character set using
two-stroke mnemonics, for instance Composeu" produced ü. An LED on the
keyboard indicated an ongoing compose sequence.

Ergonomic considerations caused the keyboard to be designed with a very
low profile; it was very thin, especially when compared to the keyboard
used on the VT100. The keyboard connected using a 4 position modular
connector over which flowed 12 volt power and 4800 bit/s asynchronous
serial data.

At the time of its introduction, the differences between the new layout
and the traditional Teletype Model 33 and VT100 layouts proved
disruptive, but the LK201's key arrangement was emulated by the even
more successful Model M keyboard and through it became the de facto
standard for all full-sized computer keyboards. Today's standard layout
differs primarily in the restoration of the Escape Key found on the
VT100 and that the numeric keypad has two double-height keys instead of
one, decreasing the number pad keys from 18 to 17. The VT220 Compose key
would survive in the European ISO standard but not in the U.S. ANSI
standard.

Follow-on keyboards from Digital refined the design introduced with the
LK201. One notable departure from the basic LK201 design was a
Unix-oriented keyboard, the LK421, that omitted the added middle group
of cursor and miscellaneous function keys but included a dedicated
Escape Key. Many Unix users preferred a narrower, ASCII-oriented
keyboard rather than the rather-wide LK201 arrangement and the Escape
Key was essential for several popular Unix editors.