Telecom-REQUEST@MIT-XX.ARPA (Moderator) (09/06/85)
TELECOM Digest Thursday, September 5, 1985 10:13PM
Volume 5, Issue 33
Today's Topics:
re: Call Conferencing
Re: Conference Calls
French phone changes
conference calls
Sprint service to Botswana and Bangladesh
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Date: Wed 4 Sep 85 21:30:03-PDT
From: John McLean <JOHN@SRI-CSLA.ARPA>
Subject: re: Call Conferencing
The problem with conferencing is that doing it properly is nontrivial.
You've got to perform the function of tieing 3 lines (the 2 phone lines and
your phone set), each having a characteristic impedance of 600 ohms. And
it is desirable to achieve balanced coupling of signals (so line 1 can hear
line 2 at the same level as he / she hears you). If one of the lines
"sees" something radically different than 600 ohms, then the party on that
line may hear an annoying echo of their voice (technical term for this is
low return loss).
If you're on a very tight budget for this, you may want to try using two
standard 2500 type phones and AC coupling the tip and ring signals (using
blocking capacitors). But this is really not a good approach since it will
mess up the characteristic impedance each line sees.
One thing you may consider is purchasing the AT&T Model 400, 2-line Adjunct
box. It does conferencing as well as line selection and call hold. And it
does the conferencing without messing-up the impedance seen by line 1 or 2.
But the box is fairly expensive ($89.00 at my local phone center store).
However, you may be able to pick up one on sale somewhere (several of us
stumbled upon a close-out of the boxes at a local store for $20.00).
I suggest you avoid the cheap conferencing boxes (available for about
$35.00). These boxes do only slightly better than you could do yourself
by capacitevly coupling your two lines using blocking capacitors.
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Date: 4-Sep-85 22:01 PDT
From: Steve Kleiser / McDonnell Douglas ISG / ASD <SGK.TYM@OFFICE-2.ARPA>
Subject: Re: Conference Calls
Although not an advertised feature, the Radio Shack 2 line controller with hold
(43-239), which has one button per line, will allow both buttons to be down
simultaneously, thus giving you an inexpensive conference calling technique
(place a call, put it on hold, push the other button, place another call, then
hold that button while pushing the 1st one down). I can't figure why they don't
advertise the feature. Maybe something un-cool about it.
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Date: Wed, 4 Sep 85 15:40:01 EDT
From: Will Martin <wmartin@BRL.ARPA>
Subject: French phone changes
Note to moderator -- don't format this -- it will get extremely garbled.
Ran across the following on USENET; thought Telecom readers might be
interested:
>From: devill@inria.UUCP (Yves Devillers)
Newsgroups: net.general
Subject: new phone numbering in France on 25/9/85, 2200 GMT.
Message-ID: <184@inria.UUCP>
Date: 28 Aug 85 19:46:11 GMT
Organization: INRIA, Rocquencourt. France
On September 25th of 1985 at 2200 GMT a new telephone numbering scheme will be
in effect in France: 8 digits phone numbers will be (in France) used instead
of 6 or 7.
>From outside France the net effect will be the following, depending on
whether you call someone in Paris area or outside Paris area:
1) Paris area:
Paris area phone numbers had a one digit area code (beginning with 1 3
or 6) and a seven digit local number.
They will have a one digit zone area (whose value will be 1) and
an 8 digit local number composed of the old area code and the old
phone number.
BUT, BEWARE, old area code 1 (Paris and close suburbs) will become
4 (cf "cnam" in exemple below, where (1) 271-24-14 becomes
(1) 42-71-24-14 ).
Exemple:
SITE BEFORE 25/9/85 AFTER 25/9/85
cnam-Paris +33 (1) 271-24-14 +33 (1) 42-71-24-14
inria-LeChesnay +33 (3) 954-90-20 +33 (1) 39-54-90-20
J. Dupont-Melun +33 (6) 010-19-27 +33 (1) 60-10-19-27
From GB, old number 0103312712414 becomes 01033142712414
From NL, old number 093312712414 becomes 0933142712414
From DK, old number 0093360101927 becomes 00933160101927
From USA, old number 0113339549020 becomes 01133139549020
2) Outside Paris area:
Outside-Paris-area phone numbers had a two digit zone area
(beginning with [2-9]) and a 6 digits local number.
They will have an 8 digit number composed of old zone area and
old phone number, without any zone area. As such no changes will be
visible from outside France.
Exemple:
SITE BEFORE 25/9/85 AFTER 25/9/85
geocub-Bordeaux +33 (56) 36-81-43 +33 56-36-81-33
imag-Grenoble +33 (76) 51-46-30 +33 75-51-46-30
From GB, old number 0103356368143 becomes UNCHANGED
From USA, old number 0113376514630 becomes UNCHANGED
NOTE: +33 is an abreviation for "dial international prefix acces then 33"
33 is the international code for France, international prefix acces
is country dependant ( 010 for GB, 09 for NL, 009 for DK,
011 for USA, 19 for F, ... )
ATTENTION:
Other new rules apply when you phone FROM INSIDE FRANCE, they are
posted inside most French phone cabine and, as such, will not
be posted in usenet.
--
Y. Devillers
...decvax!mcvax!inria!devill
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Date: 5 Sep 1985 02:26:06 PDT
Subject: conference calls
From: Eliot Moore <SWG.ELMO@USC-ISIB.ARPA>
Two-line conferencing may be fine for you, but the db loss as compared
to CO-based "3-way calling" may cause your conferencees much grief.
Modern digital conferencing boxes can compensate for said loss, but
I've yet to hear they're cost-competitive with the telco offering.
elmo
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Date: 05-Sep-1985 1207
From: covert%orac.DEC@decwrl.ARPA (John R. Covert)
Subject: Sprint service to Botswana and Bangladesh
Sprint is now providing service to Botswana (267) and Bangladesh (880).
The problem is that AT&T doesn't serve these countries, so the translations
for them are not in any No 1 ESSs -- EVEN those with equal access.
It should be dialable for Sprint equal access customers or anyone who dials
10777+011+cc... but of course it isn't.
/john
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End of TELECOM Digest
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