Originally Posted by Barrettscv

As impressive as it looks, the device is only an adjustable idler. The shifting is done manually.

The cyclist needs to put slack in the chain by using the lever to lift the idler. The cyclist then pedals backwards (the hub has a free-wheel) and use his right hand to lift and derail the chain and shift it over to the cog he/she wants. The cyclist then re-tensions the chain with the lever attached to the idler.