Editing Tandberg Data TDV 5000 Series (section)

==Unused Features==
In the non-Cherry version of the firmware, several suported features remain unused on most keyboards.

'''NOTE:''' ''While some of these points might suggest performing hardware modifications, be aware that the keyboard operates with two ground potentials. The chassis and shield around the keyboard is grounded through the shield of the cable (mains earth ground), while the electronic circuits are grounded through the commons of the cable (power ground) only. Connecting shield and circuit ground together might therefore result in ground-loop scenarios that can have unfortunate consequences to workings of the keyboard. For example, in the case of static electricity discharge, external electronic fields/noise, or if you should be unlucky and use the keyboard on a surface in the presence of a minor ground-fault. In summary, while the casing of a switch should be mounted to chassis ground, any ground for the electrical operation of the switch should be taken from circuit ground and remain unconnected with chassis ground.''

===Keyboard Mode (XT, AT, Terminal)===
By default the keyboard starts in AT-mode using scancode-set 2. However, there is code for XT-mode compatibility using scancode-set 1 only, as well as code for starting directly in scancode-set 3 (Terminal mode). Allthough the default is hardwiered on most keyboards, the mode can be set by removing the 100 ohm resistor at either ST1 (for XT), ST2 (for Terminal) or none/both of them (for AT). Eventually, patching in a 3-position toggle-switch to make a movable 100-ohm pulldown resistor, will enable this to be user-selectable.

===Beep Active by Default===
While the actuation beep feature can be toggled by the user, it is by default turned off. This is due to a 100 ohm pulldown resistor on ST3. If this resistor is removed, the beep will start out active by default. It should be possible to patch in a toggle-switch for disconnecting this pulldown by choice if you like the feature and by occasion don't want to manually enable it every time.

===Key Matrix===
The ordinary key matrix type 967043 also has a few unused switch positions: C54, D54, E13A, G01, G06 and G48A. Some of these are partially or fully covered by other keys and/or switches, some are not. Three of these corresponds to additional keys (with similar behaviour as the NOTIS-keys), two are alternate duplicate locations for existing keys, and the last one is an alternate non-duplicating location for backspace. These keys are likely features related to other, much more uncommon layouts (for example, in addition to the ordinary NOTIS-layout which is most common, Norsk Data documentation mentions there is a "Comtec" layout for Nortext as well).

====Wide backspace====
The firmware and key matrix type 967043 natively supports a double-spaced regular size backspace key. To install this, the two switches in its place (E13 and E14) needs to be desoldered, and one of them needs to be put back in position E13A. A new wide backspace keycap for the switch will also be needed.

====Keylocks====
The earlier TDV 2200 series of terminals sometimes came with two keylocks on the keyboard. Code for this can also be found in the firmware, but no known keyboard in the series has the actual keylock-switches themselves installed. The keylocks are readable from the PC using the non-standard command 0xEC, whereupon the keyboard responds with an Ack followed by a number from 0xF6 to 0xF9 depending on the keylocks' state.

The normal type 967043 matrix-board does not have any switch position for retrofitting the keylock-switches, only the corresponding diodes. Adding this feature to an existing keyboard would therefore require some patchwork or a different matrix-board.

====TDV-1200-style indicators====
The matrix-board have unused solder-pads for the lock indicator LEDs to be embedded within some of the keyswitches, as well as pads for a dual-colored indicator. Embedded LED indicators was a feature supported on the earlier [[Siemens STB 11]] switches, complete with keycaps built with a translucent window. This feature can be seen in use on earlier TDV-1200 series keyboards, and the location of the pads on the TDV 5000-series matrix board suggests that the matrix is also made to be compatible with the earlier TDV-1200 layouts/controller.