[sci.electronics] electrical cord marking/rating

jeffj@sfsup.UUCP (J.S.Jonas) (07/28/87)

[ker-zap!]

I am looking for line cords and the John Meshna catalogue
has some interesting offers.
Much to my dismay, they don't understand their merchandise,
so I ask:

"18 AWG 3 cond, SJT, 8', gray" describes a power cord.
What is "SJT" ??

	Thank you for your very kind attention.

	Jeffrey Jonas
	{ihnp4 | allegra} attunix ! jeffj

PS: I have a lot on Nixie tubes.  I love the way they glow.
Dionics makes high voltage drivers to operate plasma panels
and nixie displays.  Canal Street in NYC was a great place to
get them, but no longer.

PPS: I still have a magic eye tube that I use as a tester.

larry@kitty.UUCP (Larry Lippman) (07/30/87)

In article <1697@sfsup.UUCP>, jeffj@sfsup.UUCP (J.S.Jonas) writes:
> "18 AWG 3 cond, SJT, 8', gray" describes a power cord.
> What is "SJT" ??

	"SJT" is one of many designations used by Underwriters Laboratories
(UL) to decribe the use and insulation catagory of wire and cables.

	Common power cords made of rubber or plastic all begin with a
designation "S".  A cord designated "SJ" is a rubber cord rated at 300
volts maximum at a maximum operating temperature of 60 deg C, with an
intended application of "light duty service".  A cord designated "SJT"
is the same as "SJ", except that the insulation is thermoplastic instead
of rubber.  Most electronic equipment uses cords designated as "SJ" or
"SJT".

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
<>  UUCP:  {allegra|ames|boulder|decvax|rocksanne|watmath}!sunybcs!kitty!larry
<>  VOICE: 716/688-1231        {hplabs|ihnp4|mtune|seismo|utzoo}!/
<>  FAX:   716/741-9635 {G1,G2,G3 modes}    "Have you hugged your cat today?" 

gene@cooper.UUCP (Gene from EK Enterprises) (08/03/87)

in article <1697@sfsup.UUCP>, jeffj@sfsup.UUCP (J.S.Jonas) says:

> "18 AWG 3 cond, SJT, 8', gray" describes a power cord.
> What is "SJT" ??

Well, if memory serves me correctly (no parity errors, etc.), the SJT
refers to the plug type: two flat conductors with the semi-rounded ground
connector. Air conditioner plugs are different, for example; they have the
thicker prongs, with the two flat conductors being colinear instead of
parallel ( -.- as opposed to '.'). Oh, well...

					Gene

					...!ihnp4!philabs!phri!cooper!gene


	"If you think I'll sit around as the world goes by,
	 You're thinkin' like a fool 'cause it's case of do or die.
	 Out there is a fortune waitin' to be had.
	 You think I'll let it go? You're mad!
	 You got another thing comin'!"

			- Robert John Aurthur Halford

larry@kitty.UUCP (Larry Lippman) (08/11/87)

In article <983@cooper.UUCP>, gene@cooper.UUCP (Gene from EK Enterprises) writes:
> > "18 AWG 3 cond, SJT, 8', gray" describes a power cord.
> > What is "SJT" ??
> 
> Well, if memory serves me correctly (no parity errors, etc.), the SJT
> refers to the plug type: two flat conductors with the semi-rounded ground
> connector. Air conditioner plugs are different, for example; they have the
> thicker prongs, with the two flat conductors being colinear instead of
> parallel ( -.- as opposed to '.'). Oh, well...

	Sorry, but this is simply not correct.  "SJT", "SO", "SJO", etc.
refer to insulation type and rating of power cords, and is a universally
accepted designation system used by Underwriters' Laboratories in the U.S.
and Canada (CSA agrees).
	Plug type is another matter.  There is NO universally accepted
designation system.  Plugs and receptacles are specified by current-carrying
capacity in amperes and maximum working voltage (like 15 A @ 250 volts).
	While almost all 10 and 15 ampere @ 125 volt "line" plugs and
receptacles are interchangable, this is not true for the many variations
of plugs rated for 20 amperes and above, and for 250 volts and above.
Different manufacturers (Hubbell, P&S, etc.) use different designs for
these higher-current and higher-voltage plugs which are often physically
incompatible with those of other manufacturers rated at the same current
and voltage.
	So the point is: plugs (other than 10 and 15 ampere 125 volt line)
are generally specified by a manufacturer name and part number.
	Sometimes obtaining a mating plug or receptacle can be a real trip,
especially with Twist-Lock (tm) and similar devices.  Some vendors take
real delight in equipping their power cords with obscure connectors which
the poor end user must mate.  A personal example of this is Western Electric;
about 12 years ago my organization got a 770 PBX through New York Telephone.
This PBX came equipped with an obscure all-metal body Twist-Lock connector,
for which we had to furnish a mating receptable.  Not only did no local
electrical supply firm have the receptacle in stock, but it cost close to
one hundred dollars!  I asked New York Telephone if we could just cut off
their plug and install out own (after all, it was only 120 volts), but
of course they said "Nooooooo, this is OUR equipment and you must properly
find a mate for OUR plug."  I can just imagine some Western Electric
engineer in Denver (where the 770 was made) laughing their gonads off
every time they thought about a customer having to mate their obscure
connector!

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
<>  UUCP:  {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry
<>  VOICE: 716/688-1231       {hplabs|ihnp4|mtune|seismo|utzoo}!/
<>  FAX:   716/741-9635 {G1,G2,G3 modes}   "Have you hugged your cat today?" 

dave@onfcanim.UUCP (08/20/87)

In article <983@cooper.UUCP> gene@cooper.UUCP (Gene from EK Enterprises) writes:
>
>> What is "SJT" ??
>
>Well, if memory serves me correctly (no parity errors, etc.), the SJT
>refers to the plug type: two flat conductors with the semi-rounded ground
>connector. Air conditioner plugs are different, for example; they have the
>thicker prongs, with the two flat conductors being colinear instead of
>parallel ( -.- as opposed to '.'). Oh, well...

No, "SJT" refers to the wire itself.  The "S" means "rough Service" -
any time I've ever seen this designation, the wire was round, with an
outer insulating jacket around the three conductors (also individually
insulated).  There is also filler material in the space between the
conductor and jacket, adding strength and crush resistance.  Basically,
the wire is intended to withstand some abuse, such as it would receive
in an extension cord.

The "J" means "Junior" - a smaller version of the cable, that would stand
up to less abuse.  Compared to an "S" cable, an "SJ" cable may have
only half the insulation thickness, and is probably a lot cheaper - that's
why you don't see "S" cable very often.

Finally, the insulation jacket material is rubber by default.  A suffix
of "T" means that it is plastic ("Thermoplastic") instead.  There are
other suffixes too; the only one I can remember at the moment is "O"
for "Oil resistant".

All of these refer to the wire itself, whether it has anything installed
on the ends or not.

As for plugs, there are a variety of standard configurations for various
voltage and current ratings.  We all know what 120V 15A plugs look like
in North America.  The ones with the flat blades both rotated 90 degrees
are for 250V 15A service.