The words printed on the box

Names for plugs and receptacles

• NEMA 5-15P is the plug with two flat blades and a round ground pin, built for 125 volts and 15 amps. The P is for plug, it is on the end of nearly every cord in an American house, and our prongs are cut to this pattern.
• NEMA 5-15R is the receptacle that takes it. The R is for receptacle, and it is the outlet already on your wall.
• Duplex means two receptacles on one yoke, stacked one above the other. That is the ordinary wall outlet.
• Gang counts how many devices share a single faceplate. An outlet on its own is one gang. An outlet beside a light switch is two gang.
• Tamper resistant describes a receptacle with internal shutters that open only when both blades push in together. New construction uses them, and they take noticeably more force than an older receptacle, so a cover can feel like it is refusing to go in when it is simply stiff.
• Ground pin up and ground pin down say which way the round hole faces. Neither is wrong and both are common.

Names for cord ends

• IEC 60320 is the list the C numbers come from. It covers the small couplers that join a cord to a device, and it numbers them in pairs.
• C7 and C8 are the figure eight pair. C7 is the end on the cord, C8 is the inlet on the device.
• C13 and C14 are the squarish three pin pair. C13 is on the cord, C14 is on the device.
• Polarized means one side of the coupler is squared off so it goes in one way round only. Non polarized ends are symmetrical and go in either way.
• Inlet is the fitting built into the device that a cord end plugs into. It is not the same thing as the receptacle in the wall, and catalogs mix the two words up constantly.

Numbers about the wire

AWG stands for American Wire Gauge, and it counts backwards: the smaller the number, the thicker the copper. A 14 AWG cord has thicker conductors than a 16 AWG cord and carries more current without warming up.

On household cord sets that generally comes out as 14 AWG rated for 15 amps, around 1875 watts, and 16 AWG rated for 13 amps, around 1625 watts. The rating belongs to the whole cord and not to each receptacle on the end of it, which is the part people read the wrong way.

Length counts as well. The longer the run, the more of the voltage the wire itself uses up, which is one reason a cord no longer than you need is the better cord to buy.

Names on the jacket

Printing along a cord jacket is not decoration. It names the type of cord, the gauge of the wire, the voltage, and the laboratory that tested the design.

• SPT-1, SPT-2 and SPT-3 are flat parallel cord for indoor use, in order of increasing jacket thickness. Most household cord sets are SPT-2.
• UL 817 is the American standard that cord sets and power supply cords are tested against. CSA C22.2 No. 21 is the Canadian counterpart.
• A laboratory mark beside a standard number means a lab tested samples against that standard. The mark itself is printed on the cord or molded into the plug, so that is where to look on any cord you own.
• 125V and 13A are the voltage and the current the whole cord set is built for. Multiply the two for watts.

Words that describe rather than specify

Some words on a package are a shape or a number, and the rest are a picture. Heavy duty, slim and low profile have no measurement behind them and no test behind them either, so read them as description and go looking for the figures instead.

Thickness in inches, watts, amps, the gauge of the wire and the length of the cord are the parts you can hold up against another box and compare. Everything else is wording.