Saris PowerTap cadence sender switching
The PowerTap 2.4 speed and cadence sensor is switchable between speed and cadence
Traps for young players ...
The Saris PowerTap SL 2.4 has an optional speed and cadence sensor. It can be switched between being a speed and a cadence sensor, which is described in the instructions, but at time of writing (July 2009) the instructions for the sensor are not online. This might help anyone who got stuck.
Under the battery (CR2032) there's a small slider dip switch which selects cadence or speed as the output for the sender.