Complete sub-assembly
Provided by the ASK Keyboard Dictionary
Also known as: subassembly, internal keyboard assembly, internal assembly
A complete sub-assembly (CSA) refers to a functioning keyboard assembly that can be separated from the keyboard's cover set. "Complete" refers to how such a keyboard assembly has most of the components needs for operation such as keycaps and possibly controller card connected to it, meaning it would technically be functional without a cover set. Model B, Model F, and (most) Model M family keyboards used CSAs.