The term can be applied to a single switch or to an entire device.

There was a single large switch on the left, with a smudge of writing underneath that.

Over the top of the numbers and letters was a single red switch.

Some businesses have dozens of lights controlled by a single switch, and not all are needed at the same time.

It looks like they've got a single switch for all the primary lighting.

For many years, he had been too poor to own a boat with a single switch.

On the other side of the table was a single switch with a catch above it.

Flip the single switch, and it growls like one, too.

As though a single switch had been thrown, every light in view went out.

So as a quick fix, I don't think there's anything wrong with having a single switch that turns it all off.