telecom@ucbvax.ARPA (01/25/85)
From: Jon Solomon (the Moderator) <Telecom-Request@BBNCCA>
TELECOM Digest Thu, 24 Jan 85 16:21:20 EST Volume 4 : Issue 149
Today's Topics:
Using DTMF on pulse lines
RJ41S and RJ45S - Revisited
RJ41S and RJ45S - Revisited
PacBel leading the way
Dr.Dobbs Journal of June 85 = SPECIAL TELECOMMUNICATIONS ISSUE
RJ45S, RJ41S, RJ11C..
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Date: 23 Jan 85 10:28:47 PST (Wednesday)
Subject: Using DTMF on pulse lines
To: TELECOM@BBNCCA.ARPA
From: Bruce Hamilton <Hamilton.ES@XEROX.ARPA>
Many of you may not be aware that, even if DTMF ("touch-tone") doesn't
break dial tone on a line, you can still make some use of it if your
exchange is one which permits user entry of calling card numbers. Just
dial 0+number in pulse mode, then as soon as you hear the "bong", you
are talking to a computer, and you can switch to tone dialing and enter
your calling card number. Still better, if you're making a series of
calls, you can STAY in tone mode, enter "#" at the end of the first
call, and use DTMF to dial another number when you get the recording
"you may now dial another number".
--Bruce
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Date: 23 Jan 85 10:46:12 PST (Wednesday)
Subject: RJ41S and RJ45S - Revisited
To: TELECOM@BBNCCA.ARPA
From: John <Cottriel.ES@XEROX.ARPA>
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Subject: RJ41S and RJ45S - Revisited
To: Mark Weiser <mark@tove.ARPA>
cc: XeroxTelecom^.PA
From: John <Cottriel.ES>
Mark-
re: "...My questions are:
A. Is it likely to be a big deal or a little deal for the phone
company to install that 8-wire jack in my house? Are the 8 wires
in the wall somewhere or does a major restringing occur? (I would
guess from the descriptions of wires 7 and 8 below that they are
just a volume control from the phone company built into the box.)
B. Are there adaptors available to go from 8-wire to 4-wire connectors
and back? The quote above implies it is somehow possible.
C. What is the real difference? What are the circumstances under
which RJ-11C will not work but RJ-41S will?..."
All the wiring is done in the jacks with only two wires (tip & ring)
going all the way back to the Telco Central Office. The RJ11C
(Permissive Data Jack) in your house uses the two center wires (Tip &
Ring) for your phone. The Mode Indication and Mode Control pins are not
used. The RJ11C is actually a 6 position jack with only 4 wires in
place.
The difference between an RJ41S (97A Universal Data Jack-Fixed
Loss/Programmable) and a RJ45S-(97B Data Jack-Programmable) is that the
RJ45S is "Programmable Only", which means that the data set (modem) can
dynamically set the output level within the range of 0 to -12db, as
required. This is accomplished by a resistance within the jack that is
matched to the characteristics of the line for optimum performance at
the time of installation. This resistance appears across PR (pins 7) &
PC (Pin 8) and the modem has to have enough brains to read this
resistance and figure out what level he should transmit at. The reason
they are labeled ""Passive or isolated signal"" is that they have no
direct connection to Tip & Ring.
The RS41S jack has as a switch which is labeled FLL/PROG, that will set
the jack up as a "Programmable" as described above, or as a "Fixed Loss
Loop as described here. The "Fixed Loss Loop" option puts an H-Pad in
parallel with the Tip & Ring to provide a constant balance of power with
respect to the characteristics of the Local Loop (the line from your
house to the Telco Office) and is usually set up for 8db attenuation.
The purposes for the various jacks are to provide the correct signal
attenuation on Telco Facilities with respect to the device you are
hooking up to their stuff. Correct matching prevents crosstalk and
amplifier overdrive and therefore presents a useable signal to your
modem while allowing your modem to transmit a useable signal to the
other end. That's why they tell you that it ~might~ work on an RJ11C,
but it is not recommended. If your Local Loop is real clean, you might
overdrive the circuit (too much power on the line) and send a distorted
signal. It's not a big deal to install a data jack in your house, BUT,
the installation charge can be as much as $75. AND they might force you
to change the line from a ~Residence Line~ (~$4/month) to a ~Business
Line~ (~$8/month).
I have used an RJ41S jack connected to a modem, then plugged that into a
RJ11C jack. It will work OK if the internal resistance in the jack is
approximately matched to your phone line (Local Loop) - Good luck...
RE: "...I also think I am going to need to get myself a phoneset with
an
8-wire connector since the AJ doesn't autodial. Are these
available?..."
Sure, how much money do you have. You will need a USOC RTC Tel Set (503
for rotary dial or 2503 for Touch-Tone) You can go buy one or you can
have Telco install it for ya. If you use a Telco model you will need
these options (or use the options recommended in your modem manual)
Options are: A2, B4, [C5(touch-tone) or C6(Rotary], D8. You will also
have to give Telco the FCC Registration Number for your modem and your
TelSet (if you purchase your own.)
You'll ALSO need a RJ36X Jack installed in parallel with the RJ41S Jack
for the telset to plug into. More installation charges and more monthly
cost.
If it were my decision, I would check around for a modem that is RJ11C
compatible, that has a jack on the modem for a regular phone to plug
into and a switch to put it on line when you get the answer tone.
Racal-Vadic, Codex, General DataComm and a few others make 'em.
good luck,
John
For more information see:
Racal-Vadic Publication:
"Telecommunications From The Terminal User's Viewpoint"
Corporate Office: 408-744-0810
General DataComm Publication:
"Announcing the GDC Connection"
Corporate Office: 203-797-0711
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Date: 23 January 1985 19:18-CST (Wednesday)
From: Paul Fuqua <FUQUA%ti-csl.csnet@csnet-relay.arpa>
Subject: PacBel leading the way
To: telecom%bbncca@csnet-relay.arpa
Time as a Public Service? Here in Dallas the time service is run by
Republic Bank. Dial 844-anything and you get five seconds of
Republic-Bank-is-wonderful, then the time and temperature. No tariffs to
worry about.
pf
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Date: Wed, 23 Jan 85 21:01:21 CST
From: Werner Uhrig <werner@ut-ngp.ARPA>
To: telecom@utexas-20.ARPA
Subject: Dr.Dobbs Journal of June 85 = SPECIAL TELECOMMUNICATIONS ISSUE
[ figured this group may want get that issue. as I meet a lot of people who
are not familiar with this magazine, I'll include an overview below ]
[bugs - there is a reason for everything (I guess)]
just a quick overview, in case you missed reading page 4 in Dec 84 issue ...
NOV-84 p74 - A Guide to Resources for the C Programmer.
including a bibliography and lists of program and product
sources, this resource guide can help you start tackling the
material available.
DEC-84 the theme of the issue is "INSIDE UNIX". relevant articles are:
p24 - Varieties of Unix. a comparitive overview ov Unixes for micros
with a brief history of Unix and comments on its future,
plus a guide to choosing a Unix
p38 - Unix Device Drivers. Version 7 drivers are the point of departure
for this inside look at the Unix I/O subsystem and device
drivers.
p50 - A Unix Internals Bibliography. .. so you won't have to "grep
for it"
p96 - C/Unix Programmer's Notebook.
JAN-85 theme: FATTEN YOUR MAC - step by the step instructions to increase RAM
in the Macintosh to 512K
FEB-85 Gala Anniversary Issue 100 months of DDJ
Mar-85 theme: ARTIFICIAL INTELLIGENCE FOR MICROCOMPUTERSand announcement
of the winner of the AI-competition.
APR-85 theme: HUMAN INTERFACE DESIGN
MAY-85 theme: GRAPHICS ALGORITHM
JUN-85 theme: SPECIAL COMMUNICATIONS ISSUE
[PS: has anyone approached some of the magazine publishers to see if they are
willing to provide TOCs in advance of publication, or whenever, in
machine-readable form? I'm sure they could as they have it in their
machines, and it sure wouldn't hurt their sales. and as it is
welcome information for us that does not require typing, I'm sure
that noone would consider such postings as improper advertising.
Dr Dobbs headquarters seem to be located in Palo Alto, if someone
there wouldn't mind making a local call there to ask the question]
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Date: 24 January 1985 01:15-EST
From: Minh N. Hoang <MINH @ MIT-MC>
Subject: RJ45S, RJ41S, RJ11C..
To: TELECOM @ BBNCCA
The RJ4XS connectors are used with programmable DAAs (Data Access
Arrangement - the old term associated w/ phone connector for modems).
As you've guessed correctly, a programming resistor across leads 7
and 8 cause the modem to transmit at a certain power level. There's
a standard list of resistor values and output levels. The phone co.
technician picks the resistor to compensate for the loss through the
local loop to the central office so that your signal goes into the
network at about -13dBm (not too sure about this figure...)
The RJ11C is for permissive DAAs, ie. regular phone jacks, where the
modem agrees not to transmit at more than -9dBm. By the way, the
reference power level 0dBm is 1 milliwatt into 600 ohm load.
Mode Indicator and Mode Indicator Common are for exlusion-key operation.
If you don't have the phoneset: short them to make the modem connect
to line, open to disconnect. Actually, it is the transitions from
open to shorted and vice versa that cause the connect and disconnect.
If the modem is already dis/connected then they're ignored.
The AJ-4048 may work without the right DAA (you can insert the 6-pin
plug into the 8-pin jack) but it's best to follow AJ's instructions.
They made it.
Cheers, Minh
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End of TELECOM Digest
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