The Series 800 rotary encoder from Leine & Linde (Schaumburg, IL) has an integrated early warning system that detects worn-out ball bearings. The warning system monitors the completeness of the rotary encoder pulses and the correct pulse sequence. The error is relayed as a flashing LED on the rear of the encoder housing. The time of the fault and the corresponding error code are stored in the encoder, so the user has the opportunity to read out and analyze the error code via an RS-232 interface, once the encoder has been removed. A report can also be displayed directly at the machine, if additional wiring is added to an overriding system control.