NCR 4940


This keyboard was OEMed for NCR(National Cash Register Company)

The external appearance of the NCR 4940. The keyboard was OEMed by NMB and many other companies as well. The keyboard is a terminal-based keyboard therefore, it speaks two different protocols. One of the protocols is AT-based. This protocol has been used to make a converter see the Protocol section.

The keyboard’s layout is unique to this keyboard and is only found on another version of this keyboard that is commonly found under the NCR branding known as the ADDS ASCII:



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

Bottom of Keycap

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.


The protocol for the ADDS ASCII / 2000 can be put into AT protocol by soldering jumper wires in the following JP1-4 positions on the PCB.



Model Sticker

Main Switches

Spacebar Switches

Mold Marks




PCB Markings

ADDS Copyright