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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: electrical cord marking/rating
Message-ID: <1927@kitty.UUCP>
Date: Tue, 11-Aug-87 09:36:51 EDT
Article-I.D.: kitty.1927
Posted: Tue Aug 11 09:36:51 1987
Date-Received: Thu, 13-Aug-87 01:38:29 EDT
References: <1697@sfsup.UUCP> <983@cooper.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 46
Summary: Specifications for electrical plugs...

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
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