This keyboard was OEMed for ADDS (Applied Digital Data Systems)

The ADDS VT220 is a keyboard that is manufactured for ADDS terminals. This keyboard uses the AT protocol which is unusual for terminal keyboards. Molded feet are flush when collapsed into the back of the lower case. When extended they raise the back of the keyboard slightly. Four rubber feet help the keyboard from moving.


  • Switches

  • Keycaps

  • Upper Case

  • Mounting Plate

  • PCB

  • Back Plate

  • Cable



The keycaps are made out of PBT with dye-sublimated legends. The keycaps for the fifth generation include clips on the sides of the keycaps to secure them properly to the switch.

The keycaps on generation five boards contain wire stabs similar.

Upper Case

The upper case is made out of a single piece of beige ABS plastic. The plastic is textured due to the molding process that is used to create the upper case.

Lower Case

The lower case is molded from the same ABS plastic as the upper case. A set of slots are located in the lower case that join the two halves together. The feet that are integrated into the lower case are flush with the lower case when retracted.

Switch Plate

The switch plate is made out of stamped steel. The plate has deeper stamping around the switches so that the entire switch plate could be produced with less material. The plate is only coated with a clear coat.


The PCB is a double-sided PCB with all traces on the backside of the PCB. The controllers found on the PCB vary, some later models have been found with both Toshiba and Mitsubishi controllers.


The cable is approximately 1 meter long for the coiled variant and stretches up to 2 meters easily. It contains a molded 5 pin din connector with 6 pin headers using a molex connector on the PCB.



Model # / Jumpers




Part NO


PCB Markings