The ones I know offhand because I use them practically every day:
SPT-1, SPT-2 and SPT-3: Single Parallel Thermolastic - the number refers to the thickness of the isulation - 1 is the thinnest.
SPT-1 is usually for 18 AWG wire. SPT-2 can be used for either 18 or 16AWG wire. SPT-3 is usually for flat 3-conductor (2 plus earth) cord such as used on air conditioners.
This is also affectionally known as ZIP CORD, so when you see me use that term, this is what I'm talking about.
* A variation of SPT cord is NISPT - Non Integral Single Parallel Thermoplastic which is double insulated like the two-conductor flat European cord. This has only been on the American OEM market for a couple of years. Haven't seen it on the racks at hardware stores yet....it's usually used for the factory supplied cord for radios, TV sets and tape recorders and other such non-grounded audio/video equipment.
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SJ: Service Junior
SJT: Service Junior Thermoplastic
* Both of these are double insulated with a round cross section. I believe SJ is rubber jacketed and SJT is thermoplastic jacketed. They are also filled with fiber and paper to strengthen it.
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SVT: Service Vacuum Thermoplastic - extra flexible for use on vacuum cleaners, has a round cross section also.
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HPN: Heater Parallel Neoprene (for flat-irons, electric fires, electric toasters, etc.)
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XT: Christmas (think X-mas) Tree thermopastic - used for christmas tree wires
I just now found the list of all the UL cable designations for AC cords - it even has the insulation dimensions for the different SPT cords:
Go to this link!!
http://www.volexpowercords.com/technical_information/ul_cord_type_designations.html In fact, this link has other interesting technical documentation:
http://www.volexpowercords.com/technical_information/ Both links are from Volex, a manufacturer of cordsets.
[This message has been edited by SvenNYC (edited 12-17-2002).]