Modem Brown Box

By Phractal.


Using your modem as a bridge for two seperate lines to create '3-way 
calling'

This is a common scenario that many dialup users of the interenet have on
their computers. Many people have two phone lines at home, for the
convienience of being connected to the internet via telephone and also being
able to use the other line for voice calls.

In this diagram, we start out with two seperate phone lines, each having
their own unique telephone number of course. One line supplies Phone A with
access to a dialtone. Line two plugs directly into the modem. Almost all
telephone modems have two phone jacks. One is meant for the incoming phone
line (ie the line coming from the wall), and the other is meant to attach to
phone (Phone B), which can be used when the modem is not in use, and will
operate on the same line as line 2, naturally. This is where 'I' and 'O'
labeled on the modem come into place. The 'I' stands for input, and the 'O'
stands for output. On many modems, the input jack is labeled 'Line', and the
output jack is labeled 'Phone'. When the modem is not in use, think of it as
a router for Line 2 to Phone B.

*POTS lines from wall

   Line 1       Line 2
Phone Line   Modem Line
     |~|         |~|
      |           |
      |           |
      |           |                                /----------\
      |           |                                |          |
      |           |       /-------------\          | Computer | /----------\
      |           |       |             |          |          | | @@@@@@@@ |
    _______       \-------|<I           |          |          | | @@@@@@@@ |
   #########              |    Modem    |----------|          | | @@@@@@@@ |
  ###|___|###     /-------|<O           |          |          | \__________/
    * 123 *       |       |             |          |          |---\      /
   *  456  *      |       \-------------/          |          |  _/______\_
  *   789   *     |                                |          |
  ***********     |                                \----------/
    Phone A       |
                  |
               _______
              #########
             ###|___|###
               * 123 *
              *  456  *
             *   789   *
             ***********
               Phone B

With some tinkering, all the materials described and illustrated above can 
be
used to create a bridge of two seperate phone lines. This means that you can
call two seperate phone numbers and communicate with the people on the
recieving line at the same time, and they can hear you, and they can hear
each other, and not just you. In laymen's terms, it's three way calling. It
isn't really three way calling, because actual three calling is a service
offered by the telephone company to a single phone line, but this plan has
the exact same effect as actual three way calling. It is cheaper to have one
phone line with the three way calling plan, than to have two phone lines, 
but
if you have/need/prefer two phone lines, you can use this method to make
three way calling using two phone lines. This is totally legal as well. You
can do this same procdedure with a phone that accepts 2 lines.

To achieve this method of three way calling, setup your modem, phones and
phone lines in the following manner:

*POTS lines from wall

   Line 1       Line 2
Phone Line   Modem Line
     |~|         |~|
      |           |      /Note: Line 1 is connected to wall, and
      |           |     /       unplugged at other end
      |           |    /                           /----------\
      |           |   /                            |          |
      |           |  /     /-------------\         | Computer | /----------\
      |           | |      |             |         |          | | @@@@@@@@ |
      \-----------|-----   |<I           |         |          | | @@@@@@@@ |
                  |        |    Modem    |---------|          | | @@@@@@@@ |
                  \--------|<O           |         |          | \__________/
                           |             |         |          |---\      /
                           \-------------/         |          |  _/______\_
                                                   |          |
                                                   \----------/

    Phone A          Phone B
    _______          _______
   #########        #########
  ###|___|###      ###|___|###
    * 123 *          * 123 *
   *  456  *        *  456  *
  *   789   *      *   789   *
  ***********      ***********
       |                |
       |                |
       |                |
       |                |
       |                |
      |~|              |~|
    Line 1           Line 2

Phone A and B are both unplugged from their previous destinations. They need
to be plugged into other telephone jack terminals for Line 1 and Line 2. Be
in mind, these are still the same Lines that were mentioned before. At the
original terminal, Line 1 directly from the wall is now unplugged (but get
ready to plug into Input/Line modem jack on modem), and directly from the
wall, line two is plugged into the the Phone or Output jack.

Instructions for three way calling operation:

1) Pick up Phone B connected to Line 2 and hear a dialtone. Dial a phone
number of someone you want to speak to.

2) While talking on Phone B once they've picked up and you've confirmed a
connection, plug line 1 into the Input/Line jack of the modem.

3) You should hear a dialtone, but you are still also connected to your
friend who you previously called. You can still hear eachother if you speak
loud enough over the dialtone. This dialtone is the dialtone of Line 1.

4) Pick up Phone A, which is connected to Line 1 and dial a number of 
someone
you wish to speak to. You should hear the tones of the numbers being dialed
on Line 2/Phone B, as well as Phone A of course. The dialtone will stop
as it always does once you enter a DTMF tone.

5) If all goes well, and the third party picks up, both of the people can
talk to you, hear you, and hear eachother, hence three way calling.

***NOTE***
With step  4, you can dial the third party directly from your second line, 
or
in this case, Phone B. I told you to dial from Phone A because it better
illustrates how this works.

Also, reset to original setup to get online :)

~~~Why this works.~~~

The Output jack for the modem also accepts input over a phone line, because
otherwise, how would you talk to someone on a phone routed through a modem,
without them hearing you. Your voice is the input.

The Modem thinks that the lines you connected in diagram 2 are one phone
line. And since the Line 2 is connected to the output modem jack and then to
the wall, instead of an individual phone, the modem is now in essence,
'connected' with the rest of the phones all hooked up to line 2.

The thing that triggers the whole thing is when you connect line 1 to the
modem. Now, I'm not totally sure why this part happens, but I think it's the
modem trying to figure all of this out. So here's my hypothesis: The modem
recognizes that there is activity on Line 2, so it opens up the Input jack
for information automatically, and therefore, you get an auto-dialtone when
you insert Line 1 into the 'Line/Input' Modem jack. The modem is basically
taking the phone off the hook on the Input jack. And it's all ready for you
once you insert Line 1.

Slackware ownz!

--Phractal
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