Editing Siemens TA-BS/1200 (section)

==Description==

This is the keyboard ("TA"="Tastatur") for the Siemens T1200-BS Teleprinter, which was in production from 1986 till 1991. Except for its military cousin T1285, the T1200 series was the last series of telex machines introduced by Siemens, in a period, where the telex service became replaced by telefax and email. In the late eighties, there where three models available, Standard (SD), Economic (EC), both of which where compact units with a line display and built-in keyboard, and "Bildschirm" (BS, "monitor"), which looked like a PC with its separate components: central unit, monitor, matrix printer - and the keyboard that is presented here. Except for their respective population with switches and LEDs, the keyboard modules were the same for all three models, but only the BS had it detached from the main unit and equipped with a controller board. The T1285 cousin has a keyboard that looks quite similar to the BS one.<ref name="crypto" />

Around 1990, the BS model was phased out in favour of the CT ("computer") model, which could also be used as a PC, with a rubber-dome keyboard in the style typical for Siemens at the end of the eighties.
The rugged T1285 remained in production beyond 1995, with three models: Shielded (Z), Shielded Cryptographic (ZC), and Cryptographic Applications (CA), which also was available in a cream-coloured variant for office use.

The keyboard module is mounted inside a snap-in case, which does not need any screws whatsoever. When mounted inside the main unit (SD and EC models), the big holes in the top left and right corners of the plate are used for screwing it in. White-slider [[Siemens STB 21]] A2113-A5 switches are used for the alpha section and short-travel grey-slider A2133-A5 switches for the function keys. The unlabelled shift-lock key has a [[Siemens STB 11|STB 11]] switch with an integrated green LED (which STB 21 switches don't support). Earlier versions had all STB&nbsp;11 switches of the heavier variant, also then using the corresponding short-travel variant (D32) for the function keys.<ref name="svcman" /> The function keys have short travel so that their caps don't get stuck in the narrow openings of the case, and to provide them with a more keypanel-like feel to the user. All momentary switches are equipped with diodes, and the board has NKRO. The [[double-shot]] keycaps are the Siemens-typical stepped type for the alpha keys including the space bar. The keyboard has two 3.5 cm flip-feet, the connector is 15 cm short.

There are a total of 16 LEDs for status indication; they were necessary since the SD version only had a single-line display. Due to the large number of LEDs, some of them are not directly connected to controller pins but are driven by an addressable latch, and the key matrix columns are multiplexed by decoder ICs. A symmetric V.11 serial connection links the controller board with the main unit.

The keyboard can be adapted to customer needs, with custom keycaps and additional keys. With some national variants, the switch in the shift-lock position is used to switch between Latin and Arabic, Cyrillic or Greek mode. The position of the Delete key seems unusual from a computer perspective, but is familiar from some typewriters. The keys T1 and T2 in the position where other boards have Backspace could be programmed with short texts. The REP key in the top left is pressed along with other keys to make them repeat. The SEITE key in the bottom left corner scrolls page-wise.