Mike, Just to add a few more words of explanation from an outsiders persepctive for you.
The pins are the same shape and size on all 120 and 240V plugs rated for 15 and 20A. It is the pin configuration which differs. If you look at the chart provided in Ron's link, the normal 120V 15A type is NEMA 5-15 which has parallel pins. The 240V 15A version is type 6-15, in which the pins are turned through 90 degrees to be in line.
The 20A versions of each have one pin set at 90 degrees to the other (types 5-20 and 6-20). The 20A receptacles for each have one slot T-shaped. In other words, a 120V 15A receptacle will accept only the corresponding 15A plug, but a 120V 20A outlet will accept either a 15 or a 20A plug. The same with the 240V versions, but of course the arrangement of which pin is turned through 90 degreees is different to prevent 120 plugs entering 240 outlets and vice versa.
The other types common in residential wiring are 10-30 or 14-30 for dryers, and 10-50 or 14-50 for ranges.
By the way, the term duplex refers to a device with two receptacles on the same yoke -- What in other countries might be called a double or twin socket.
[This message has been edited by pauluk (edited 05-13-2003).]
I wasn't sure if or how the term Duplex was used outside the US and thought that might be misunderstood. I was going to hunt down a picture of a Duplex and Single Receptacle, but hadn't had the time yet.
Guys, Thank you all for your help regarding this subject. Ron, Thanks for the link to the plug diagrams, I never new that there were so many different combinations!. Paul, I thought that Duplex was a term that meant Two phase!?.
Let's face it, these days if you're not young, you're old - Red Green
I see you're hedging your bets over another thorny issue in these photos by having one ground up and the other ground down!
Trumpy, You might not be aware that the term duplex is also used in America to refer to two homes constructed as a single building. These are what would be called "semi-detached" in Britain -- Not sure what you call them down under.
indeed the word duplex it show up alot around here in usa. not only electral related items but other stuff also like duplex pump ( two pump in one unit) etc etc .. same with singleplex sometime i called uneplex ( short term french for single unit) but the other hand about grounding pin for both singleplex et duplex it been hot debate in few forum not only one here but few other electrican forums too have simuar debates and we end up with one answer just use the common sense the code dont say anything about grounding pin is up or down. mainly depend on the plugins itself that all but can debate more later
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)