Date: Mon, 5 Oct 92 16:20:19 CST
From: Jack Decker <Jack@myamiga.mixcom.com>
Newsgroups: comp.dcom.telecom
Subject: Re: A Good Way to Play a Micro Tape Over the Phone?
Organization: TELECOM Digest
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 12, Issue 764, Message 1 of 4

In message <telecom12.749.2@eecs.nwu.edu>, aa571@cleveland.Freenet.Edu
(Gail  M. Hall) wrote:

> Here is the situation.  I have a call-in dictation system that doctors
> can use to call in to dictate their reports for me to type.

> However, some doctors still like to use their little dictating
> machines that they can carry in their pockets and would like their
> secretaries to play the tape over the phone into my system.

> Normally this is a very unsatisfactory process because the machine
> they use is very "low-fi" and then with the relatively low fi from the
> phone line, what we end up with is a mess.

Audio-to-audio coupling (holding the speaker of the recorder to the
telephone microphone) is almost guaranteed to produce poor results.

> I have seen those little gadgets in stores that can attach to the
> phone line and that you can attach a recorder to to record a
> conversation over the phone.  What I am wondering is:

> 1.  Can you reverse that little gadget to go through the phone line
> by PLAYing it instead of on record to play the tape from the office
> in order to avoid room noise, etc.?

Only maybe.  Depends on the circuitry inside the unit.  Try plugging
the microphone plug into the earphone/speaker output on the recorder,
and adjust the volume while you listen in on another phone on the
line.  If you can hear the audio clearly, it should work.  When
sending down the line, the audio you hear on your end should be
slightly ABOVE normal conversational volume (the same as when someone
else is talking on an extension phone on your line ... normally, you
hear them at a much louder volume than the person on the other end of
the call).

> 2.  If not, is there somewhere an INEXPENSIVE gadget that will do the
> same thing?  My dictation system dealer does not know of such a
> product.  They make the little hand-held machines, the transcribers,
> and the phone-in dictation systems, but not a thing like I am
> interested in.

> This would need to be an inexpensive item.  Doctors are not going to
> want to pay big bucks for this as they have enough big bucks expenses
> to worry about.

Yeah, those tennis club memberships and greens fees aren't cheap!  :-)

(My apologies if you work for some good doctors.  At this point, I
hold doctors as a class in only slightly higher esteem than
attornies ... but there is a difference ... there ARE a few good
DOCTORS still around.)  :-)

Seriously, here is a circuit I've used with good results, for both
recording AND playback of tapes from/to the phone line:

      +-------+---------)||(------------||----------> phone line
      |       |         )||(          .1 uf
      |   .02 =   8 ohm )||( Hi Z
      |    uf |         )||(          .1 uf
  o---O-------+---------)||(------------||----------> phone line
  plug               transformer

Parts List (and explanation):

plug - plug to fit the earphone/speaker and/or microphone jacks on
     recorder
 .02 uf capacitor, any available voltage... helps eliminate radio
     frequency noise (from nearby transmitters, floursecent lights,
     etc.) from the recording.  Probably not necessary on playback only
     unit.
 .1 uf capacitors (2) - prevent DC from the phone line from saturating
     the transformer.  Mylar capacitors are recommended, and should be
     rated at 200 volts or higher.  Higher values (e.g. .5 uf or even 1
     uf) are probably even better as long as the voltage rating is high
     enough AND the capacitors are non-polarized (don't use
     electrolytics!).  However, you don't want to go TOO high or you
     may drain off so much of the audio signal that you'll be unable to
     hear on the phone.
Audio transformer - one side is 8 ohm (typical impedence of a speaker)
     and the other side is a higher impedence.  The unit I used came
     out of an old tube-type television set and I believe had an
     impedence of 10K or so on the Hi-Z side, but I imagine other high
     values might work.  If you have an old audio transformer lying
     around and you know which side drove the speaker, by all means try
     it (the speaker side should be the Lo-Z side).  Note that you
     DON'T want to try to the phone line if you're using this as a
     recording device, since matching the phone line would cause a loss
     in audio level on your telephone.  HOWEVER, if you are using the
     unit for PLAYBACK ONLY, then you may want to try making the Hi-Z
     side of the transformer 600 ohms and eliminating the two .1
     capacitors...  this should allow the user to hang up the phone
     while playing back the tapes.

Electronic purists will probably be having fits at my callous
disregard to impedence matching, but all I can say is that the unit as
pictured has worked very well for me in the past!  If you don't feel
you have the expertise to build one, ask any ham radio operator or
electronics wizard you know for help ... this should be a pretty easy
circuit to construct for anyone who knows how to handle a soldering
iron (I was building stuff more complicated than this when I was 12
years old!).

> When doctors can use the phone my setup works very nice.  There are
> some, though, that would really rather use their hand-held machine and
> let the secretary send the whole tape via phone at one time.

That should not be a problem as long as they use some sort of direct
connection to the phone line.

By the way, if you want to get REALLY cheap and dirty, and can't find
anyone to build the above circuit, and have phones where the
mouthpiece can be unscrewed and the tape recorders are BATTERY
OPERATED (very important!  You don't want them connected to the AC
power line if you try this!), you could go to Radio Shack and get a
"patch cord" with one end that has a plug that fits the
speaker/earphone output on the recorders, and the other end with two
alligator clips.  

Try plugging the patch cord into the recorder, unscrew the phone
mouthpiece, and clip the alligator clips across the exposed microphone
contacts.  Then adjust the volume as required by listening to the
earpiece (in this case you're looking for a normal volume level).  If
THAT doesn't produce good results, you could also try unscrewing the
EARPIECE and clipping across the two screw terminals on the earpiece
and see if that sounds any better.  But even if it works, eventually
you're going to want to find a better method of injecting the audio
into the phone line.

DISCLAIMER: Since none of the suggestions involve FCC registered
equipment, I will not even attempt to guarantee that the above advice
is both legal and does not violate telephone company tariffs.  So,
either try these suggestions on a private phone system, or understand
that some phone companies might not care for you trying these things
on their lines.  Also, be aware that shoving excessive audio signal
down the line could cause crosstalk and other undesirable effects, so
use only a high enough volume setting to produce a comfortable
listening level.


Jack Decker    jack@myamiga.mixcom.com    FidoNet 1:154/8