Method/apparatus for performing the following acts on a system that includes an electrical motor followed by a gear, and a speed output unit: monitoring a first set of frequencies from the system over a measurement period when the system is in a known good operating condition; storing the first set of monitored frequencies or derivatives thereof as reference data in a long-term storage system; monitoring a second set of frequencies from the system over a measurement period when the system is in an unknown operating condition; comparing the second set of monitored frequencies with the first set of monitored frequencies in a frequency domain; in the frequency domain, detecting changes between corresponding frequencies resulting from the second set of monitored frequencies and the first set of monitored frequencies.