"Because of the finite size of clumsy human fingers, it had no more controls than that of its ancestor of three hundred years earlier. There were fifty neat little studs; each, however, had an unlimited number of functions, according to the mode of operation - for the character visible on each stud changed according to the mode."
http://www.technovelgy.com/ct/content.asp?Bnum=1267
"Because of the finite size of clumsy human fingers, it had no more controls than that of its ancestor of three hundred years earlier. There were fifty neat little studs; each, however, had an unlimited number of functions, according to the mode of operation - for the character visible on each stud changed according to the mode."