Safe-T-Lock programmable code switch prevents unauthorized use of machinery. Superior Signals STL1000 allows up to 99 different users to be input for tracking machine usage. If an accident or damage occurs, the last operator is readily identified. An internal clock records "on" hours and notifies the operator when the vehicle reaches the 250-hour mark. A 4- to 8-digit personal access code can be chosen for each user, and a separate supervisor user menu can be used to program the unit.