Engineering, wiring

Engineer comes back with some very useful responses, this one on the diff between 14/2 and 14/3

http://able2know.org/topic/308109-1

In this connection I'm looking for a device that I'm not sure exists but if it does what's it's called: It would have various forms, probably the most popular a disc placed under the bulb in an outlet, or a loose 2-wire device placed in series with the load

It might be programmed in several different ways, but typically it toggles on and off so as to provide sequencing to appliances. Suppose in the former instance you have two bulbs in different rooms controlled by a single switch, but you don't always want 'em both to be on at the same time. Typically then they'd sequence as (1) Room 1 only; (2) Room 2 0nly; (3) Both on (4) Both off

I imagine a huge market for gadgets of this sort and so I've supposed it already exists; though I don't know what it's called