System (20) with a safety lock (21), the safety lock (21) being configured to at least partially prevent use of a surgical instrument (22). A foot switch assembly (1) is operably configured to control the surgical instrument (22), and has multiple switches (4; 10; 14; 15; 16). A memory (26) is present for storing a predetermined switch sequence associated with the switches (4; 10; 14; 15; 16) of the foot switch assembly (1), as well as a control unit (25) configured to determine whether a series of input switch actuations from the foot switch assembly (1) corresponds to the predetermined switch sequence, and if so, deactivating the safety lock (21) in response to the series of input switch actuations corresponding to the predetermined switch sequence. The invention also relates to various embodiments of a foot switch assembly for controlling a surgical instrument.