From: rbook@owlnet.rice.edu (Robert Aaron Book)
Subject: Re: Phone/Audio Line Facts
Organization: Rice University
Date: Tue, 24 Nov 1992 02:23:46 GMT

In article <BxL33C.Es9@cmptrc.lonestar.org>, carter@cmptrc.lonestar.org (Carter Bennett) writes:
|> There seems to have been a recent rush of people wondering about 
|> connecting phone lines to audio lines.  I'm suprised nobody's chimed in
|> yet.  Phone line interfacing is a snap!  I'll skip the bulk of the theory 
|> and get into the meat of it.
|> 
|> You will need:  20Kohm - 600 ohm telephone line transformer 
|> 		capacitor, value not critical - 0.001 to 0.010 uF 60-70VDC
|> 		potentiometer (5 or 10 kohm perhaps)
|> 		hookup wire
|> 		switch (optional)
[...]
|>    See?  Simple!


If you don't like messing with transformers, capacitors, and the
like, here's an easier bus slightly less elegant way:

Get a phone with one of those handsets you can unplug.  Aside from
this, you need the following:

1.  A phone line "splitter"  (a little gadget that lets you plug two
    phones into one line -- usually use for extension phones, or a phone
    and an answering machine or something like that).  Should cost about
     $2.50 at a drugstore, Radio Shack, Target, etc.  (See parentheses
    for step 3 below to see if you also need a coupler.)

2.  An RJ-11 Crimping kit.  Far less intimidating than it sounds.  This is
    a scissor-shaped device that lets you attach those phone plugs to phone
    wire.  I got mine for $6.50 from Wal-Mart, and that included more than
    enough plugs for this and several other projects.  Be sure to get one
    that can handle both RJ-11 line cords (that connect the phone to the 
    wall) and the smaller handset plugs (that connext the phone to the
    handset).  (You can even do the project without this if you make the
    right modifications and buy both a new hanset cord and a phone cord
    with jacks on both ends.  This is uglier and slightly more expensive.)

3.  Some phone cord.  It will not take much.

4.  1/8 inch or 1/4 inch plugs.  Your preference, depending on your 
    equipment.  Should be mono rather than stereo, but this isn't too
    important.  1/4 inch plugs are 2 for $1.50 at Radio Shack.  You'll
    want two of them probably.


Now, do the following:

1.  Take a length of phone cord, and crimp a small handset-size plug on 
one end and a larger line-size plug on the other end.  Alternatively,
take a pre-existing phone cord with the plugs attached and cut one plug
off and replace it with a hanset plug.

2.  Unplug the handset cord from the phone side.  Plug the handset-plug side
of the cord from step 1 into the phone's handset jack. If you didn't get the
crimper, plug one end of your new handset cord into the phone.

3.  Plug the other end of the cord from step 1 into the single side of the
splitter.  (Some splitters have a plug on one end and a jack on the other.
If this is the case, you'll need a coupler as well -- an inch-long device with
two jacks.  Another $2.50, from the same place where you got the spliter.)

4.  Plug the free end of the handset cord into one of the two jacks on the
splitter.  The handset itself should be on the other end.  (Yes, you
are plugging a "small" handset-size plug into a "large" line-size jack.
It will work, but you have to stick the plug in perfectly straight.  If
you are a purist, you can cut off the handset cord plug and crimp a 
line-size plug on the hanset cord.  The cord is the same.  This is optional.)
Now, test what you've done so far.  Pick up the handset and you should hear
a dial tone.  If the phone is plugged in.  :-)

5.  Now, get another length of phone cord and crimp a line-size plug onto
one end.  If you didn't get the crimper, cut one plug off of the line cord you
got.

6.  Strip the outer insulation off of the other end of cord from step 5.  This
should reveal four individual wires -- Red, Green, Yellow, Black.  Strip these,
but leave enough about two inches of the colored wires unstripped and visible.

7.  Attach the Red and the Green from setp 6 to the two terminals on the 1/4 
inch or 1/8 inch plug.  Which color goes to which terminal is irrelevant.
This is your audia output from the phone, which you will use to record or
patch into your transmitter.  See note (*) below. If you will only be putting 
sound into the phone, you can skip this.

8.  Attach the Black and Yellow to the two terminals of the other plug, like
in step 7.  Again, which is which doesn't matter.  This is your audio input
to the phone, and you can use it to play radio, tape, etc., into the phone.
If you don't want to do this, you can skip this step.


Notes:

(*)  I have not actually plugged this into mic input on a tape recorder, so 
I'm not sure it'll work.  The reason is my tape recorder doesn't have a mic
input.  My tape recorder does, however, have a dual cassette with dubbing
(copying) capability, and this is $20 away from being just as good.  You can
get a little device called a "CD Cassette Adapter" for about $20 from Radio
Shack or an audio store.  This has a stereo earphone plug on one end of
a wire and a thing that looks like a tape cassette on the other.  (This intent
of the product is to enable you to listen to CD's in your car if your car
has a tape player and you have a protable CD player.)  Put the cassette end
into the play-only cassette deck or in a cassette player hooked into your
transmitter or whatever.  To plug the plug end into the phone, you'll need to 
either use a jack instead of a plug in step 7, or get a coupler, which is
essentially two jacks end-to-end ($1.50 from Radio Shack). In this case, to
get the mono signal to come through both left and right on a stereo system,
you'll also need a mono-to-stereo adapter ($1 from Radio Shack).  Now,
your stereo will think your copying tapes, but you'll actually be recording off
the phone!  Be sure to use "Normal" instead of "high-speed" dubbing.

Possible Problems:

1.  Everyone you show this plan to will tell you it won't work.  People tell
me this even after I've been using it for weeks.  I *know* the setup described
in (*) above will work.

2.  If you are using a mic input instead of (*), please tell me whether or 
not it works.  (rbook@rice.edu, (713) 661-2775)

3.  When you record using the phone so equipped, your voice will be louder
than the other party's.  I am workign on this, and would appreciate any
suggestions.

4.  There are no beeps or anything to tell the caller you are recording.  This
may be illegal if the caller doesn't know he/she is being recorded, so be sure
the caller knows and consents.

5.  When playing music into the phone, keep the volume low.  This is not
music-on-hold, since you can talk over it, but this setup could probably be
adapted for this purpose.





I use the above to record phone interviews for the weekend news program 
on KTRU, the student radio station at Rice University.  The sound quality 
isn't perfect, but it is good enought to broadcast.

--Robert Book         News Director, KTRU 91.7 FM (Houston, TX)
  rbook@rice.edu      (713) 661-2775


3.  When you use this telephone
Newsgroups: alt.radio.pirate