This device is commonly used in bathrooms here in countries that use USA style wiring devices & practices.
Nowadays it's supposed to be GFCI-protected if used in a bathroom:
The switch and socket are independent devices but depending on how it's wired you can have the switch control just a lightbulb, just the socket or both. The third screw on the left side is a ground (earth) terminal.
I don't like them. They're expensive to replace and it only gives you one socket. This example costs almost anywhere from US$7.00 to $10.00 at D-I-Y sheds and hardware stores.
A regular duplex receptacle can be had from anywhere from 50 cents for the really cheap & nasty "residential grade" garbage, to US$1.50 or $2.00 for a good-quality heavy-duty "commercial grade" device.
Industrial and hospital-grade devices cost more, naturally but the "commercial" devices are an excellent price/quality compromise. And it allows you to plug in two appliances at the same time, so you're kind of minimizing the potential use of usually bad-quality triple-taps.
It would be better for the end user to have basic, easily obtainable and replaceable devices that don't cost much.
Keep in mind that if something breaks, the typical customers you have in mind are more likely to want to tackle the repair job themselves because they probably can't afford to hire a "licenced professional."
I have a Malaysian-made BS-546 5-Amp socket with a switch. It's a self contained unit mounted on a plate and the connections between the hot side of the socket and the switch are concealed with a non-removable plastic cover.
The switch only controls the socket....and there's only one set of terminals that are used to attach wires to the socket.
[This message has been edited by SvenNYC (edited 02-25-2004).]