On Friday 03 July 2009, arne anka wrote:

quoted text
> >> Hm, i was always under the impression that most bike systems use a

> >> simple magnet and a reed switch (no need for hall effect sensor) for

> >> both cadence and speed measurements. So any sensor from a regular

> >> "bike computer" can be directly attached to the mic line of FR.

> >

> > They do, and they eventually fail

>

> how?

The same as any other mechanical switch - operation becomes unreliable leading

to inaccurate speed measurement, then fails completely. It doesn't happen

quickly - it was on the second or third set of batteries so it would have been

several years and thousands of miles.
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