Editing BTC 51 series (section)

==Series==
Confirmed models according to the user's guide are 5139, 5149 and 5169; 5140 is included for convenience, and the exact scope of this series is not known for certain. Model 5139 is not to be confused with the totally different [[BTC 5139 series]]. Three separate FCC IDs have been found associated with keyboards in this style.

The 5130 and 5131c keyboards by Packard Bell use a different chassis, but the same switches as the mainline 51 series. 71, 72, and 79 series of keyboards are related, use the same switches, and very likely the same PCBs.

Other brands that used these series of keyboards as a basis of theirs include Wyse, Commodore (owned by Tulip), Laser, and possibly others.

Note that later BTC 51 series changed to the much cheaper rubber dome over membrane design with no sliders, many of those keyboards have a hollowed-out looking back, and the M in their name possibly indicates that these are membrane models. They also often came in differently styled chassis than the older mainline models.