The activation switches on each ANH lightsaber comes from different brands of calculators.

As a key was pressed on these calculators, the LED chip would display the number and the bubble lens would magnify the digit so it could be read easier.

The image on the right shows a comparison of a real 7 digit display and a Blast-Tech replica made from clear resin. The real calculator strip is shown on the bottom.

Here is a breakdown of which calculator displays were used in which sabers:

There is a very slight difference between the Extracta models 19 & 20. Because of the lack of good reference material on the original lightsabers, we are unsure as to which of these models was originally used.