So this guy asked me how to get digitized Macintoshª sounds into a modem, so he
can play them over the phone line during a conversation. Lions roaring when he
calls customer service, that sort of thing...

The simple answer is, it canÕt be done. Most modems donÕt have the necessary
digital-analog-converter (DAC) circuit. Voicemail units, like the DoveFax+ª, are
another story.

But every Mac has a DAC built-in! ItÕs what beeps, boings, and insults you with
Talking Mooseª. You just need to connect it to your phone.

A few months ago, I posted a circuit that would let you connect any Macª to
almost any phone circuit. Since then, IÕve been e-mailed countless letters of
thanks (well, more than two). But some folks asked for more:

ÒWhy canÕt it be louder?Ó ÒWill it work with stereo sounds in my newer Mac?Ó ÒHow
can I use it with my home stereo or Walkmanª?Ó ÒWhat is the meaning of life, the
universe, and everything?Ó

For the answer to most of these questions, read on...

---------------------------------------------------------------- STEREO? LOUDER?

Original Macs (most compact models, from the 128 up through the SEª series) had a
low-current audio output jack: it worked well with an amplifier, but didnÕt have
enough oomph [technical term] to drive headphones. So the first circuit I devised
just matched that output to the phone system. It wasnÕt particularly loud, but it
worked with any Mac.

Newer Macs have a more powerful output jack. So I modified the circuit to use
that power to boost the voltage going to the phone. At the same time, I doubled
it so you could use it to pick up both sides of stereo sounds (theyÕll be mono on
the other end of the phone line, of course), or to connect your phone to a stereo
amp or tape player.

Which circuit fits your Mac? You can tell by plugging a pair of headphones into
the back. If they play in stereo with full volume, use Circuit II. If they sound
kind of wimpy, use Circuit I... and donÕt leave the phones plugged in.

---------------------------------------------------------------- CIRCUIT I

Read this even if youÕre building the other version. Some of the descriptions
apply to both.

YouÕll want a circuit like this:


Ê









IÕve included Radio Shack¨ stock numbers, but you should be able to find
equivalent items at any electronic store or hackerÕs closet.


PLUG - 1/8" mini plug to fit your Mac. Compact Macs and older Mac II models with
mono output can use a 2-conductor plug, #274-286.

SWITCH - Any single-pole, double-throw switch. #275-635 is a good possibility, or
you can use knife switches, three-way wall switches, or block switches from the
model train you abandoned when you bought a computer.

TRANSFORMER - This is the key to the whole thing. It keeps the Mac and The Phone
Companyª from interfering with each other. If you donÕt use one, youÕll probably
disable your phone service.

Any low-power 1:1 audio transformer should work. You can rip one out of that
300-baud modem youÕve been meaning to toss, or get a #273-1374 for under four
bucks.

(If you get the Radio Shack transformer, cut the Scotchª tape wrapped around it
to free up the four wires. The wire colors should match the diagram.)

CAPACITOR - This isnÕt necessary for transmitting sound, but it lets you hang up
your phone. Otherwise, the phone system will think the transformer is an active
telephone.

Get a film or ceramic capacitor rated at least .1 µF at 75 volts. Slightly higher
ratings arenÕt a problem. #272-1053 (.1 µF / 200 volts) is a good choice.
Electrolytic capacitors wonÕt work.

SPEAKER (optional) - Using the sound output of your Mac disables its internal
speaker. Pull the plug out to turn the speaker back on. Or wire in a substitute,
#40-246 (or any other small low-power speaker, like the one from that 300-baud
modem). It wonÕt be as loud as the internal speaker, which could be a good thing.

YouÕll also need some hookup wire, to extend the components and reach your
telephone. Use bell wire, #278-1509, or anything else in your basement or on
Radio ShackÕs shelf.

---------------------------------------------------------------- CIRCUIT II

Build one of these:

Ê










The parts are the same, except the transformers are audio-output stepdown ones,
used backwards. Radio Shack #273-1380 does the job nicely. (YouÕll need two of
them, but theyÕre cheap.)

The plug should be a stereo Òring-tip-sleeveÓ one: #274-284 matches newer Macs
and most Walkpersons; use #274-139 for most home stereo amps. Or rip the cord off
a pair of non-functioning headphones.

I left the switch and speaker off the drawing of this circuit, but you can add
them if you want. You can also leave out one transformer, if youÕre dealing with
a mono circuit (but _donÕt_ tie the tip and the ring of the plug together; that
can harm your Mac).

The transformer color codes might change, so follow these simple rules:

1.     Note how one side of the transformer has two wires, and the other has
three. The two-wire side connects to the Mac. The three-wire side faces the
phone. The middle wire on the three-wire side doesnÕt connect to anything.

2.     Note how white is wired to white, and green is wired to green. Even if you
use transformers with different colors, the two sides of the stereo circuit must
match. Otherwise, stereo sounds will be mangled and mono ones will disappear
entirely.

---------------------------------------------------------------- CONSTRUCTION

Both the MacÕs audio output and the standard phone system are low-voltage.
Special wiring techniques arenÕt needed.

Solder or twist the wires together neatly, and insulate the connections with
electrical tape (or even duct tape, Scotch Tapeª, or Band-Aidsª).

It doesnÕt matter which wires go where on the speaker or capacitor. If youÕre
using a stereo plug (circuit II), notice how the middle wire goes to the tip of
the plug, the top wire goes to the ring partway up the plug, and the bottom wire
goes to the plugÕs sleeve.

Follow the color codes, and Ñ if youÕre using a switch Ñ make sure the wire from
the Mac goes to the switchÕs center connector.

Put the whole mess in a box to make it look pretty. I used part of an old
intercom: the speaker and switch were already built in.

---------------------------------------------------------------- CONNECTION

The Mac end is easy. Plug it into the jack that has a speaker icon, like this
one: Ê


You have a few choices when it comes to the Telephone end.


1.	DIRECTLY TO THE PHONE JACK	Open up the jack on your wall (itÕs low
voltage). YouÕll see at least one red and one green wire, connected to screw
terminals. Connect a wire from the transformer to either of these screws, and
from the capacitor to the other screw.

2.	DIRECTLY INTO THE PHONE		If youÕve got a standard, non-electronic,
non-memory phone, open it up and trace the wires coming in from the back. TheyÕll
connect to two screw terminals marked L1 and L2. Connect the two wires from your
circuit to these screws. It doesnÕt matter which goes where.

3.	JUST PLUG IT IN				Get a phone cable like #279-391, with a
standard modular plug on one end and four short wires coming out the other.
Connect the transformer and capacitor to the red and green wires. Then plug the
modular end into any standard phone jack or modular Y-connector.

4.	FOR MULTI-LINE PHONES 		If your office phones have thick cables and
1A2 multiline connectors (they look like SCSI plugs), get a #43-270 adapter. Then
use method #3, above.


Digital phones Ñ found in some office buildings Ñ require a special jack. Look on
the bottom of your office phone. If thereÕs a ÒRinger Equivalent NumberÓ or ÒRENÓ
stamped on it, itÕs NOT digital and you can use these methods. (Touch-Toneª
phones arenÕt necessarily digital.)

Office telecom managers can help you get the right jack, if they can keep from
laughing uncontrollably when you describe what you want to do.

--------------------------------------------------------------- OPERATION

Make a phone call. Play a sound on the Mac.

If you donÕt hear the sound on your telephone handset, flip the switch.

Set the volume with the Sound Control Panel.

---------------------------------------------------------------- AUTHORÕS NOTE

The trademarks herein belong to companies with big law firms.

The circuit should work and be safe. I tested both versions (and have built many
for friends) and never had any problems. However, strange things can happen to
Macs, lightning can strike phone lines, and klutzes can burn themselves with
soldering irons. So I donÕt guarantee anything.


Jay Rose

Co-author ÒFirst Book of MacintoshÓ [Sams / Alpha]; wrote chapters on Sound and
some other stuff in ÒEverything You Wanted to Know About the MacÓ [Hayden].
Contributing editor (on audio, what else?) to Desktop Video World. Buy my books,
please.

America Online: JC Rose CIS 71174,2044 
