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From: varney@ihlpf.att.com (Al L Varney)
Newsgroups: comp.dcom.telecom
Subject: Re: Questions About New Service Being Installed
Message-ID: <telecom11.262.6@eecs.nwu.edu>
Date: 1 Apr 91 02:20:05 GMT
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X-Telecom-Digest: Volume 11, Issue 262, Message 6 of 11

Oops!  Some corrections:

In article <telecom11.246.5@eecs.nwu.edu> varney@ihlpf.att.com (Al
"Oops" Varney) writes:

> [In other articles, Fred R. Goldstein and Jim Rees write:]
 
Fred> The 1ESS has relays in it, not to do the actual switching,
Fred> but to switch ringing voltage and the like on to the loop.  It makes a
Fred> lot of noise, although nothing like a panel office!

  This is correct, in the sense that the "switches" are not "relays".
 
Jim> The 1ESS (and the 1A, which uses a less antiquated processor) uses
Jim> reed relays to do the actual switching.  They're vacuum-sealed, so
Jim> they're quieter than the old ones.  I suspect that the 1 can do Caller
Jim> ID too, though Im not sure.
 
>   The No. 1 ESS Switch indeed uses sealed relays for the switching

      But I meant to say "reed switch" here ^^^^^^

> fabric, but "reed relays" ???  Nope.  The actual T/R path is through
> magnetic-latching relays, surrounded with some metal and a coil.
                    ^^^^^^
        ...and here          

> Pulse the coil one way, the contacts close and REMEMBER to stay
> closed.  Pulse the other way, the contacts open and REMEMBER to stay
> that way.  No current is used to maintain either position.

  I E-mailed a better explanation to Jim, but in summary, the reason I
disagreed about the term "reed relay" was because of the word "relay";
but then I used it myself (Ooof)!  They are "switches" because they do
not actually switch a current based on another current or pulse.  They
are switched "dry" (sans current); the contacts can't be cleaned and
will stick or weld shut if switched "wet" frequently.  Therefore,
external relays to trunks and lines must be used to remove battery/
ground before setting up a path through the network.  A matrix of
switch crosspoints is arranged so that closing a tip/ring crosspoint
in a matrix automatically opens all the other pairs in the same X row
and Y column.  When a path is "released", it's X and Y matrix points
are marked idle, but the crosspoints remain closed until some other
action selects another crosspoint in the same X row or Y column.

Further errata:

> Instruction set vaguely resembles an orthoganal version of 1E, with
   No "Freudian" jokes, please... it's ^^^^^^^^^^ "orthogonal".

> a typical instruction (24 or 48 bits wide) taking .7 milliseconds.
                         let's try "microseconds", eh? ^^^^^^^^^^^^

>Al Varney, AT&T, Lisle, IL

  You really ought to read the stuff before you publish, dum-dum.

 Al