Key Tronic KB 3270 Plus Keyboard
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SVG images to see the keyboard layouts.
The KB 3270 Plus is a 122-key keyboard, for use (like the
IBM 1397000) as a terminal emulation
keyboard on the PC. Judging by comments in the published source code, it
appears that this, or a similar model of keyboard, was the one used when
support for function keys F13-F24 was added to Windows NT 3.5.
Unlike the IBM keyboard, the KB 3270 Plus supports both AT and XT
communication protocols. It also has three different layouts. Both
layout and protocol are selected using DIP switches.
The three layouts are:
- Native
- IRMA emulation
- Enhanced 101 Scan Code Set. This comes in two variants: 'Enhanced 101' (US)
and 'Enhanced 102' (International).
A number of alternative keycaps are provided for the three layouts. This
image shows it with the 'Enhanced 101' keycaps.
In addition to the standard layouts, the keyboard can also have a custom
layout; it is supplied with two utilities, SE to edit a set of
scancodes, and SL to load them into the keyboard. I believe that
this ability is what distinguishes the KB 3270 Plus from the
vanilla KB 3270.
The keyboard has a 5-pin XT / AT style connector. Mine was also supplied
with a passive converter allowing it to be connected to a PS/2 socket.
Hardware
The keyswitches, as usual for a Key Tronic keyboard, are capacitative
foam-on-foil, and will doubtless succumb in time to perished foam.
The controller is an 8051. Other components on the board include an 8k
ROM containing the firmware, 8k of static RAM, a beeper, and a chip marked
C5145B connected to the key matrix, which I presume handles the capacitative
sensing.
Unlike on an IBM / Unicomp keyboard, there are no 'hidden' key positions
without keys above them.
LEDs
The keyboard has the usual three LEDs. These are set in the keys they
apply to, rather than in a separate panel.
DIP switches
The keyboard has eight DIP switches:
- Switch 1
- Switch on to use XT protocol, off for AT.
- Switch 2
- Switch on to select IRMA scancodes.
- Switch 3
- Switch on to select Enhanced 101 / 102 mode.
Switches 4 and 5 alter behaviour in the Enhanced 101 / 102 mode:
- Switch 4
- Switch on to filter out E0 xx scancodes.
- Switch 5
- Switch on for international layout (Enhanced 102),
off for US layout (Enhanced 101).
- Switches 6, 7
- Unused.
- Switch 8
- Switch on to enable key click.
Keycaps
The KB 3270 Plus is supplied with enough keycaps to set up three different
layouts, corresponding to the three supported sets of scancodes. The first
layout is the 'Native' layout: