The supply voltage for the speed sensor must be supplied through the electric line which is lead outside.

It is a TTL-signal from the raw data of the sensor at the drive motor of the treadmill.
There is no information and no calculation of the speed so that the signal is available completely unaltered.
Based on a possible visualization of rising and falling edges of the impulses, you can here determine slightest changes of speed
without any average determination algorithm and without any delay.