TELECOM@Usc-Eclb (08/07/82)
TELECOM AM Digest Saturday, 7 August 1982 Volume 2 : Issue 99
Today's Topics:
Lauren Gets Top Billing
Poached Modems And Modular Plug Polarity
The Mapping Of Area Code 202
Query: Origin Of The Term "Repeater" - Myth or Fact?
800 NPA & Some Very Random Boston Area Prefixes
----------------------------------------------------------------------
Date: 6 August 1982 0056-PDT (Friday)
From: lauren at UCLA-Security (Lauren Weinstein)
Subject: poached modems and modular plug polarity
To: TELECOM at ECLB
Greetings. Regarding the fried Vadic modem... Telco line protectors
(which are actually just fuses, of course) are designed to prevent
"excessive" voltages from reaching the subscriber side of the line
drop. Their only real purpose is to prevent loss of life, and *not*
necessarily to protect delicate equipment. In most cases, voltages
which are more than sufficient to fry semiconductor circuitry would
*not* be considered to be "excessive" from a protector standpoint.
Also, the average telephone set is rather robust by most standards and
can survive considerably greater surges than more delicate equipment.
Of course, the newer "electronic" phones often are very vulnerable to
surge damage.
One other point: it is entirely possible that the damage was caused by
induced currents in the wiring of your building from the lightning
strike. In such a case, the protectors wouldn't even be involved,
since they only have an effect on surges coming down or going up the
drop itself. In any case telco is not legally responsible for any
damage to subscriber- owned equipment in such a situation, since
negligence is not an issue.
There are some firms who manufacture "transient protectors" that might
be able to help in such situations. They tend to be regularly
advertised in many computer periodicals. Versions exist to provide
A.C., RS-232, and phone line protection. Such devices usually rely on
varistors, gas-discharge tubes, and thermal circuit breakers for
"three-mode" protection against most types of surges.
---
Regarding the "modular plug blues"... Under normal conditions, the
TIP side of the phone line is GREEN and is POSITIVE with respect to
the RING (RED) side of the line. When a modular plug carries two
lines, the *convention* is for the second line to have TIP on the
YELLOW wire, and RING on the BLACK.
Indeed, the pin orientation of modular plugs do reverse at many
connect points, which certainly makes it rather difficult to deal with
polarity sensitive equipment in any uniform sort of fashion. The
usual solution to polarity problems is simply the judicious reversing
of TIP/RING where necessary on equipment or modular cords themselves.
There isn't much else that can really be done, except for the
installation of bridge rectifiers in the actual equipment (which would
probably have had bridges already if it had been properly designed!)
--Lauren--
------------------------------
Date: 6 Aug 1982 0814-EDT
From: John R. Covert <RSX-DEV at DEC-MARLBORO>
Subject: 202 mapping
Let's get this right, once and for all.
Area Code 202 is Washington, D.C., 703 is Northern/Eastern Virginia,
and 301 is Maryland.
Those codes WITHIN the District (plus the OXford CENTREX, which is
officially located within the District, even though most of the phones
in it are in Virginia at the Pentagon, Fort Myer, the Navy Annex, and
Cameron Station) are in area code 202 ONLY.
Those codes in 703 and 301 which are in the "Washington Metro Dialing
Area," i.e. which are local to D.C. AND each other, can also be
reached from anywhere on the network with 202 as well as their correct
area code. The rate and route data base has all the correct info for
each NXX, so the call is billed the same regardless of which area code
is dialled.
Codes in 703 or 301 which are only local to the District and not to
the ENTIRE Metro area can be dialed only with the correct area code.
There is one anomaly. If you are in Maryland or Virginia and are
using an INTERstate outwats, you may be able to reach those INTRAstate
points in the D.C. suburbs on YOUR own side of the Potomac by dialing
202. This will work only if the exchange providing WATS service does
not 6-digit translate the 202 area. Exchanges will normally only
6-digit translate an NPA when the exchange itself has two different
routes it would use to that area. Normally six-digit translation of
distant NPAs is only done at the toll switch, which can't tell an
outwats call from any other.
Knowingly making an INTRAstate call on an INTERstate outwats is
probably toll fraud.
------------------------------
Date: 6 Aug 1982 17:52 EDT
From: Axelrod.WBST at PARC-MAXC
Subject: Query: Origin of the Term "Repeater" - Myth or Fact?
I just heard an interesting explanation of how the term "Repeater"
came to be used for a telephone line amplifier. I'll pass it along
for the amusement of all, and I'm wondering if any of the telephony
historians out there can confirm or refute it.
In the early days of telephony, there was not enough signal strength
out of a handset to make long distance calls. If a subscriber needed
to have a conversation with someone distant, the operators would patch
connections through as many CO's as was necessary. An operator stayed
with the call at each CO. Then, since the original signal couldn't
complete the entire circuit, the operators themselves would relay the
conversation by repeating each statement and response, back and forth,
throughout the duration of the call.
Well, after a while, some bright chap invented an electronic amplifier
(vacuum tube, I assume) that would allow the signal to make long
circuits without excessive attenuation. The human "repeaters" were
replaced by Electronic Repeaters.
It's a cute story. Does anyone know if it's true?
Art Axelrod
------------------------------
Date: 5 Aug 82 11:23:00-EDT (Thu)
From: Carl Moore (VLD/VMB) <cmoore@BRL>
cc: cmoore at BRL
Subject: "800" prefix
I have read in this digest about upcoming changes (?) to the way "800"
prefixes are assigned, and (also figured from other sources) about
prefixes of the form NN2 only being used for INTRAstate "800". I
have now come across an ad (phone number verified by calling 800-555-
1212 and asking for the number to use from area 302) which has 800-782
prefix for calls from outside Nevada.
------------------------------
Date: 6 Aug 82 10:23:43-EDT (Fri)
From: Carl Moore (VLD/VMB) <cmoore@BRL>
cc: cmoore at BRL
Subject: Boston area prefixes
On page 8 of call guide in 1982 Boston white pages, there is a list,
by exchange, of business office phone numbers. The exchanges include
several of the "area code" (N0X and N1X) type, and I am confused.
This is in 617 area.
[Hmm, I saw those in the 1982 Boston area white pages too. The
number's don't work yet, as well as I can tell. The exchanges are:
801, 802, 803, 804, 806, 807, 810, 811 (!), and 814. I too am confused
(which isn't surprising). --JSol]
------------------------------
End of TELECOM Digest
**********************
-------