My sink is in the island, and does not have a wall switch to start the disposal.
I had an older model InSinkErator, used for 21 years without problems. That switch was in the drain plug having
 to click the switch on inside the drain when I turned the plug.
The new model InSinkErator has a magnet that turns the disposal on and off when I turn the sink drain plug. 
It is much easier to use and so far, I like it much better! 
Great change in design!