Tellerwerk has a test set-up whereby the meter can be tested functionally at all rpm. Tellerwerk does this by means of a variable rpm motor and photocell. Reading out the results is done with a frequency meter. Depending on the meter ratios de tachometer can be tested and adjusted when necessary. Speedometers can be adjusted by time units with alternating rpm in the same way. Upon request a functioning diagram from the restored meter can be made.