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NMB desktop membrane keyboards

NMB are notable for a widely-used style of membrane switch using a proprietary-mount plunger over rubber dome. In time, the use of a separate plunger was phased out. Production of desktop membrane keyboards ended in 2015 when NMB left the keyboard market.



Travel for the membrane types is given as 0.140±0.020″ (3.56±0.5 mm), which is exactly the same as the figure given for the Series 725 mechanical series RT-8200W.

Tentatively it appears that keyboard lifetime was dropped from 20 million to 10 million cycles between 1997 and 1999 for lower-end models:

Model Lifetime (Feb. 1997) Lifetime (Feb. 1999)
RT-4900W 20 million
RT-6600W 20 million 20 million
RT-6800W 20 million 20 million
RT-9100W 20 million 20 million
RT-9500W 20 million
RT-2200W 10 million
RT-2700W 10 million
RT-2900W 10 million
RT-5100W 20 million
RT-9200W 10 million
RT-9600W 20 million

The general specifications are the same across all models, although rated lifetime varies by model:

Model RT-9100W RT-2200W RT-2700W RT-2900W
Full travel 0.140±0.020″ (3.56±0.5 mm)
Pretravel 0.090±0.020″ (2.29±0.5 mm)
Operating force 2.0 oz nominal (55 gf)
Rated lifetime 20 million cycles 10 million cycles
Legend printing Unspecified Laser etched Laser marked
Switch type With discrete plunger Not depicted
Contact material Unspecified Mylar with silver–carbon overlay


The documents are mostly marked with a code such as “KB10/98”, which is taken to be the month and year that it was written. The PDFs themselves were archived by the Wayback Machine in later years.