Speed control / Central Vac's

[Chris Hunter <cjhunter@xxxxxxxxxxxx>]

'wondered what sort of speed control might work on a central vacuum
cleaner motor unit ... not only to run quieter, but also because
we've run a 50mm pipe out to a covered but open-to-the-west sitting-
out shed (maybe gazebo is the right word) and it would be good if the
HA could be set switch it on from time to time at a low setting, to
provide some ventilation in a cushion box we've built under the
seats, so the cushions etc will stay reasonably dry ... ??

Chris