218 lines
8.7 KiB
Plaintext
218 lines
8.7 KiB
Plaintext
So this guy asked me how to get digitized Macintoshª sounds into a modem, so he
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can play them over the phone line during a conversation. Lions roaring when he
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calls customer service, that sort of thing...
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The simple answer is, it canÕt be done. Most modems donÕt have the necessary
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digital-analog-converter (DAC) circuit. Voicemail units, like the DoveFax+ª, are
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another story.
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But every Mac has a DAC built-in! ItÕs what beeps, boings, and insults you with
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Talking Mooseª. You just need to connect it to your phone.
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A few months ago, I posted a circuit that would let you connect any Macª to
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almost any phone circuit. Since then, IÕve been e-mailed countless letters of
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thanks (well, more than two). But some folks asked for more:
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ÒWhy canÕt it be louder?Ó ÒWill it work with stereo sounds in my newer Mac?Ó ÒHow
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can I use it with my home stereo or Walkmanª?Ó ÒWhat is the meaning of life, the
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universe, and everything?Ó
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For the answer to most of these questions, read on...
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---------------------------------------------------------------- STEREO? LOUDER?
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Original Macs (most compact models, from the 128 up through the SEª series) had a
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low-current audio output jack: it worked well with an amplifier, but didnÕt have
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enough oomph [technical term] to drive headphones. So the first circuit I devised
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just matched that output to the phone system. It wasnÕt particularly loud, but it
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worked with any Mac.
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Newer Macs have a more powerful output jack. So I modified the circuit to use
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that power to boost the voltage going to the phone. At the same time, I doubled
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it so you could use it to pick up both sides of stereo sounds (theyÕll be mono on
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the other end of the phone line, of course), or to connect your phone to a stereo
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amp or tape player.
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Which circuit fits your Mac? You can tell by plugging a pair of headphones into
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the back. If they play in stereo with full volume, use Circuit II. If they sound
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kind of wimpy, use Circuit I... and donÕt leave the phones plugged in.
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---------------------------------------------------------------- CIRCUIT I
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Read this even if youÕre building the other version. Some of the descriptions
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apply to both.
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YouÕll want a circuit like this:
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Ê
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IÕve included Radio Shack¨ stock numbers, but you should be able to find
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equivalent items at any electronic store or hackerÕs closet.
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PLUG - 1/8" mini plug to fit your Mac. Compact Macs and older Mac II models with
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mono output can use a 2-conductor plug, #274-286.
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SWITCH - Any single-pole, double-throw switch. #275-635 is a good possibility, or
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you can use knife switches, three-way wall switches, or block switches from the
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model train you abandoned when you bought a computer.
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TRANSFORMER - This is the key to the whole thing. It keeps the Mac and The Phone
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Companyª from interfering with each other. If you donÕt use one, youÕll probably
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disable your phone service.
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Any low-power 1:1 audio transformer should work. You can rip one out of that
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300-baud modem youÕve been meaning to toss, or get a #273-1374 for under four
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bucks.
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(If you get the Radio Shack transformer, cut the Scotchª tape wrapped around it
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to free up the four wires. The wire colors should match the diagram.)
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CAPACITOR - This isnÕt necessary for transmitting sound, but it lets you hang up
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your phone. Otherwise, the phone system will think the transformer is an active
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telephone.
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Get a film or ceramic capacitor rated at least .1 µF at 75 volts. Slightly higher
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ratings arenÕt a problem. #272-1053 (.1 µF / 200 volts) is a good choice.
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Electrolytic capacitors wonÕt work.
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SPEAKER (optional) - Using the sound output of your Mac disables its internal
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speaker. Pull the plug out to turn the speaker back on. Or wire in a substitute,
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#40-246 (or any other small low-power speaker, like the one from that 300-baud
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modem). It wonÕt be as loud as the internal speaker, which could be a good thing.
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YouÕll also need some hookup wire, to extend the components and reach your
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telephone. Use bell wire, #278-1509, or anything else in your basement or on
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Radio ShackÕs shelf.
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---------------------------------------------------------------- CIRCUIT II
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Build one of these:
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Ê
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The parts are the same, except the transformers are audio-output stepdown ones,
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used backwards. Radio Shack #273-1380 does the job nicely. (YouÕll need two of
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them, but theyÕre cheap.)
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The plug should be a stereo Òring-tip-sleeveÓ one: #274-284 matches newer Macs
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and most Walkpersons; use #274-139 for most home stereo amps. Or rip the cord off
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a pair of non-functioning headphones.
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I left the switch and speaker off the drawing of this circuit, but you can add
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them if you want. You can also leave out one transformer, if youÕre dealing with
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a mono circuit (but _donÕt_ tie the tip and the ring of the plug together; that
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can harm your Mac).
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The transformer color codes might change, so follow these simple rules:
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1. Note how one side of the transformer has two wires, and the other has
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three. The two-wire side connects to the Mac. The three-wire side faces the
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phone. The middle wire on the three-wire side doesnÕt connect to anything.
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2. Note how white is wired to white, and green is wired to green. Even if you
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use transformers with different colors, the two sides of the stereo circuit must
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match. Otherwise, stereo sounds will be mangled and mono ones will disappear
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entirely.
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---------------------------------------------------------------- CONSTRUCTION
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Both the MacÕs audio output and the standard phone system are low-voltage.
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Special wiring techniques arenÕt needed.
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Solder or twist the wires together neatly, and insulate the connections with
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electrical tape (or even duct tape, Scotch Tapeª, or Band-Aidsª).
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It doesnÕt matter which wires go where on the speaker or capacitor. If youÕre
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using a stereo plug (circuit II), notice how the middle wire goes to the tip of
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the plug, the top wire goes to the ring partway up the plug, and the bottom wire
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goes to the plugÕs sleeve.
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Follow the color codes, and Ñ if youÕre using a switch Ñ make sure the wire from
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the Mac goes to the switchÕs center connector.
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Put the whole mess in a box to make it look pretty. I used part of an old
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intercom: the speaker and switch were already built in.
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---------------------------------------------------------------- CONNECTION
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The Mac end is easy. Plug it into the jack that has a speaker icon, like this
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one: Ê
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You have a few choices when it comes to the Telephone end.
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1. DIRECTLY TO THE PHONE JACK Open up the jack on your wall (itÕs low
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voltage). YouÕll see at least one red and one green wire, connected to screw
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terminals. Connect a wire from the transformer to either of these screws, and
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from the capacitor to the other screw.
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2. DIRECTLY INTO THE PHONE If youÕve got a standard, non-electronic,
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non-memory phone, open it up and trace the wires coming in from the back. TheyÕll
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connect to two screw terminals marked L1 and L2. Connect the two wires from your
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circuit to these screws. It doesnÕt matter which goes where.
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3. JUST PLUG IT IN Get a phone cable like #279-391, with a
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standard modular plug on one end and four short wires coming out the other.
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Connect the transformer and capacitor to the red and green wires. Then plug the
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modular end into any standard phone jack or modular Y-connector.
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4. FOR MULTI-LINE PHONES If your office phones have thick cables and
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1A2 multiline connectors (they look like SCSI plugs), get a #43-270 adapter. Then
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use method #3, above.
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Digital phones Ñ found in some office buildings Ñ require a special jack. Look on
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the bottom of your office phone. If thereÕs a ÒRinger Equivalent NumberÓ or ÒRENÓ
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stamped on it, itÕs NOT digital and you can use these methods. (Touch-Toneª
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phones arenÕt necessarily digital.)
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Office telecom managers can help you get the right jack, if they can keep from
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laughing uncontrollably when you describe what you want to do.
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--------------------------------------------------------------- OPERATION
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Make a phone call. Play a sound on the Mac.
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If you donÕt hear the sound on your telephone handset, flip the switch.
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Set the volume with the Sound Control Panel.
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---------------------------------------------------------------- AUTHORÕS NOTE
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The trademarks herein belong to companies with big law firms.
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The circuit should work and be safe. I tested both versions (and have built many
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for friends) and never had any problems. However, strange things can happen to
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Macs, lightning can strike phone lines, and klutzes can burn themselves with
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soldering irons. So I donÕt guarantee anything.
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Jay Rose
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Co-author ÒFirst Book of MacintoshÓ [Sams / Alpha]; wrote chapters on Sound and
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some other stuff in ÒEverything You Wanted to Know About the MacÓ [Hayden].
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Contributing editor (on audio, what else?) to Desktop Video World. Buy my books,
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please.
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America Online: JC Rose CIS 71174,2044
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