Introduction: Telephone Handset Microphone

Picture of Telephone Handset Microphone

Some time ago my girlfriend asked me if I would make her one of those telephone microphones like the kind that all of those hipster bands have. So, I of course told her I would. Much time passed... and then I made this.

This is designed to work with the old-style handsets with the carbon mics inside (see picture). It probably won't work with most newer handsets.

I'm sure twelve year olds in 1994 used to call this a "purple polk-a-dot box." I apologize for my |33t h@><0r ignorance.

Step 1: Go Get Stuff.

Picture of Go Get Stuff.

What you will need:

1. Terminal-Block Cover (Radioshack Part #279-455)
2. AA battery holder (Radioshack Part #270-401A)
3. Micromini Toggle Switch (Radioshack Part #275-624)
4. 1/8" Mono Jack (Radioshack Part #274-251)
5. 1 AA battery
6. 2-5/8" x 2-1/4" cover (aluminum, plastic, cardboard, etc...)
7. 3/16 x 1" nuts and bolts (or one size shorter)


1. 1 roll black gaffers tape
2. 1 roll white gaffers tape


1. Soldering iron
2. Hot glue gun
3. Drill (3/16 and 15/16 drill bits)
4. Flathead screwdriver
5. Needle nose pliers
6. Wire stripper

Step 2: Prepare the Case.

Picture of Prepare the Case.

With your pliers, break out the little tabs on the bottom of the case so that the battery holder can lay flat on the bottom.

Once the plastic tabs are removed, drill a 3/16" hole in the side of the case at a right angle from the phone jack. This will be for the toggle switch (see picture)

Next drill a 15/64" hole in the bottom of the case opposite the phone jack. This hole will be for the 1/8" mono plug (again, see picture).

Take the 2-5/8" x 2-1/4" piece of material. This will be the lid to your case. Drill a 3/16" hole in your lid approximately 1-1/4" inch in from each side (see picture). Measure your material for better measurements and better results.

Step 3: Solder!

Picture of Solder!

Solder the circuit as shown in the picture.

If you do not like looking at pictures, then follow these simple instructions:

The red wire on the battery holder goes to the toggle switch. The black wire from the phone jack also goes to the toggle switch.

The black wire from the battery holder goes to the ground terminal on the 1/8" mono jack. The yellow wire from the phone jack goes to the other terminal on the 1/8" mono jack.

Step 4: Debug.

Picture of Debug.

Put in a battery. Plug in a phone handset. Connect it with an audio cable to a speaker and make sure it works (don't forget that the toggle switch might be in the off position).

If it does not work, check your wiring. Make sure the connections are good and the connections are right. If both of those are good, then check to see if your phone handset works and looks like the one shown below. If you still can't figure out the problem then put in a new battery. If that is a no go, check to see if your speaker is turned on, the volume is up and you plugged the mic in to the right jack. If none of that works, you may have an audio device that requires a 1.2V line-level input. Try using a different audio device or see Step 8. If you have tried everything and you still can not get it to work, get someone else to do it for you.

Step 5: Install the Components.

Picture of Install the Components.

With your hot glue gun, glue the battery holder to the inside of the case opposite from the holes for the switch and the jack. Take the nuts off your switch and jack, put the two components through the holes you made for them and screw the nuts back on, fastening them in place. Clip the unused red and green wire.

Step 6: I Lied About the Circuitry!

Picture of I Lied About the Circuitry!

My initial design has no voltage protection (the thing that you were building up until now).

So, realizing that this lack of voltage regulation is a problem, I built the circuit pictured below to kick down the output voltage from 1.5 to 1.2 volts (because rumor had it that this was line level). Line level is still a bit myserious to me, but thanks to a comment posted on the main page by Phatso I can now tell you that line level is probably more around 1v. However, the circuit below should still work fine.

Put together the circuit shown below and shove it inside your case (so that your mic works right and doesn't harm any other devices that you plug it into).

You can also try just using a 100K potentiometer and a 10uF electrolytic capacitor between the telephone jack and the mono jack. This, in theory, will provide volume control and protection from bad voltages. However, I'm not really sure how or even if this will work. This is mere speculation on my part (based on what someone told me once in passing).

Also, a low voltage LED to indicate whether the device is on or off may be nice.

Step 7: Optional Beautification.

Picture of Optional Beautification.

If you are like myself and cut out an aluminum cover out of a much larger sheet of aluminum, then you have a small piece of conductive metal with some nasty edges. You are going to want to both cover and insulate this to prevent injury or the rare crossed wire. More importantly, you are going to want to cover it so that it does not look ugly.

To solve all of these problems at once I wove a checker board pattern out of thin strips of black and white gaffers tape.

I started with the tape stuck to the back side and folded it over and under until the whole front side of the lid was covered. Going in one direction were all of the white pieces of tape, one next to another, and in the other, the black. The pictures below might help you understand better.

This whole weaving process can be maddening. Figure out what works for you. There is no right answer. You can make any pattern you want. Just make sure that both sides and especially the edges of the lid are covered.

If you are working with a material that does not have sharp edges and is non-conductive, you may want to consider decorating your case in some manner any which way.

Punk rock!

Step 8: Closing the Case.

Picture of Closing the Case.

Now your box should be more or less done.

If you covered over the 3/16" hole in your lid, now would be the time to poke through the covering.

If you have not removed the screw that came with the case, now would be the time to do that.

Taking the 1" bolt, screw on a nut all the way to the bottom and then insert it into your case. Put the bolt through the hole in the lid. Fasten the lid to the to the case with a nut, tightening it with your pliers if need be.

Step 9: Perform "Sweet Jane" (words and Music by the Velvet Underground)

Picture of Perform "Sweet Jane" (words and Music by the Velvet Underground)

The only way to complete your telephone handset microphone is to perform "Sweet Jane" with your new microphone and the instrument of your choice.

Words and chords can be found here:

You can view my performance here:

(Be warned! My video camera broke and I had to resort to a really bad stop motion animation.)

Please post a link to your performance.


Gigean (author)2014-12-20

I'm having trouble tracking down a phone like this-- anyone have any suggestions?

KennethJ21 (author)Gigean2016-05-03

found these all built no batt.

kerikino (author)2011-03-29


Houdinipeter (author)kerikino2011-06-26


mcguyverzboss (author)2011-05-30

Great project. A definite improvement of one of my attempts with retrofitting old phones. Have you tried using a three/four pin jack connector and wired the speakers up as well. It would make a completed usable phone. It seems a waste to have the speakers not in use. Keep up the good work!

Yerboogieman (author)2010-07-01

Well a big Hello to you, Mr. Sarafan. I want to wire my telephone handset to a phone input. The colors on the phone wire are Red, Black, Yellow, and Green. The wires on the 3.5mm cellphone input are colored Red and Gold, and the other set of wires is White and Gold. Do you know which wires to connect? Thanks. Here is a bit of a description on what I'm trying to do.

Oops, it is a 2.5mm plug.

comradebrandon (author)2010-05-27

how would this be different if i wanted to wire the mic instead of the receiver? 

randofo (author)comradebrandon2010-05-27

What do you mean?

ryguy9 (author)2010-05-09

howdy, thanks for this :D
i can't hear anything except for static when i blow into it, which i find kinda strange...
any pointers?
thanks :D

randofo (author)ryguy92010-05-10

This is going to sound kind of strange, but try bashing your mouthpiece against a hard surface a few times (this loosens the crystals - or something of the sort). If that doesn't help, perhaps try another handset. If that doesn't work, perhaps you accidentally wired it wrong? Or the connection with the jack is bad? Maybe the signal is too hot (high voltage) for your amp? Do you have a picture of it? 

Logan D (author)2009-12-28

 This looks like it has some potential to become a DIY (and pretty shotty) bullet mic for harmonica playing

Yerboogieman (author)2009-10-12

Yeah, I looked up line level, it is hard to understand. Indeed mysterious.

Full Frontal Graphic (author)2008-03-26

If the mic on these old phones stops working, you can take it out and slam the edge against someting solid a couple of times and then shake it real hard... ... lots of times it will work when you put it back into the handset. I have no idea why this works, just that I have resurrected dozens of phones with this trick, which was taught to me by a 4th grade kid about40 years ago. Only works with those old phones, don't try it with the new "hi tech" phones .

That's because sometimes the carbon granules in the "cup" essentially get clumped. Banging the element around loosens them back up.

Right, 'cos the new 'high tech' phones have what are called piezo condenser microphones.

oatmealfight (author)2007-11-11

Hey there, I really like your project! I seem to be picking up an FM signal along with my voice. Did this happen to you? What can I do about it?

If you're getting FM signals, a temporary solution is to touch the ground connections. You won't get shocked, trust me. However, if you're running your circuit on something higher than 12 volts, then ignore what I just said.

randofo (author)oatmealfight2007-11-11

errrr.... nope. Try checking your solder connections to see if any of the connections might accidentally be touching. It's hard to tell what the problem might be without being able to see it.

stratcat (author)2008-09-04

You're definately on the right track. Adding a resistor will prevent smoking the carbon element in case of a short (yes, I've done it!). And a capacitor will keep DC out of your amplifier. The resistor can be 680R-3K3 and the cap can be .01 to 1uF. Neither are critical Drawing included.

doog (author)2008-08-30

I, too, would like more explanation of this part.

randofo (author)doog2008-08-31

What in particular is confusing you?

doog (author)randofo2008-08-31

personally, I've never dealt with building circuits before, but I've read up some and have gotten a better understanding of this diagram. But, a picture of your circuit would be helpful.

Sonic Surgeon (author)2008-08-29

Check mine out.. Quite a bit different than yours, but principally the same thing. I added a few tweaks on the inside.

mwintner1 (author)2008-06-22

is there any way i could skip the box thing and directly connect the wires from the phone to a "guitar cable"?

natepalm138 (author)mwintner12008-06-27

you can. it's seems simple enough. we did it. splice the guitar cord, they're will be a bunch of bare wires surrounding another wire in the middle. the inside is in is the "hot" or, when it comes to the telephones mic "hi" it should be labeled somewhere. just take the phone's mic out (it should be a speaker with some kind of incasement) pop the speaker out and there we'll be 2 flat metal ehhh, "things" on the incasement sticking up towards where the speaker was before you removed it. just solder the "hot"(inside) guitar cord wire to the "hi" "metal thing" on the phone's speaker's casing. snap it back together and your done. no battery needed! **make sure to test the hot to hi before soldering by wrapping the wires around the metal connectors and snapping it back together and testing it through an amp** I don't know what happened to ours but for some reason the cord went out and it wont work anymore. BUT IT WORKED WELL WHILE IT DID!! another way to try is soldering the wires directly to the mic (hot to middle, ground to outside like this (picture) let me know how it all works out. message me at: if you have any questions.

mwintner1 (author)mwintner12008-06-22

my phone never had a wall plug or battery, so i'm not sure where the voltage was coming from. anyway i was wondering if i can do this project without a battery (or pots/resistors)

sehrgut (author)mwintner12008-06-22

Nope. The carbon mic is a variable resistor. A modern phone would have an electret mic, which actually produces a signal on its own without a power supply. Telephones were always powered by the phone company over the phone line. A simple enough phone can still manage that, by the way . . .

luck (author)2008-06-02

what voltage resister will i need and were do i wire it

luck (author)2008-05-30

I also found out that the phone has a 9 volt cord. would I be able to wire the 9 volt cord to the wirering diagram and the phone if I were to wire the power in the loop or do I still need to use a separate battery. Another question I have is if instead of tapping into the speaker if I could use your original plans but instead of wirering directly into the microphone I could wire to the microphone receiver and use the regular power cord to power the phone and a battery for the microphone signal, or will I not need a battery if this wirering idea is possible.

randofo (author)luck2008-06-02

If you connect 9V, to the power cord going into the phone, you shouldn't need any other power sources or batteries. The phone should operate fully (except for ringing). If you need to get audio from the speaker, you just need to connect the speaker wires to an audio out jack (or so I'm guessing). However, you might need to add a resistor in series to decrease the voltage of the signal.

luck (author)2008-05-30

What do you mean tap into the speaker? Could you explain.

luck (author)2008-05-29

is it possible to use a wireless phone. If so then what do i do? do i just wire it the same way and keep the power cord to the phone pluged in so that it will work. Or will the battery alone work. your help would be greatly apreciated. This mic will help me to record my invention ideas before i foget them.

randofo (author)luck2008-05-29

You would just have to power up the phone completely with a 9V battery and then tap into the speaker to get audio out.

luck (author)2008-05-29

is it possible to use an LED that will use enought voltage when your mic is on so that u can get the voltage closer to the line level without having to build a totally different circuit.

randofo (author)luck2008-05-29

You might be able to find some low-voltage (1.5v) LEDs, but they are somewhat rare. Try using to search for that.

tk421dan (author)2008-04-10

Randofo, (I hadn't seen this before I posted mine) ah, your's is prettier then mine to boot, oh well , good job and thanks for the link to your Instructable!

cimz (author)2008-02-16

hey guys i've followed this wiring diagram shown except i have replaced the 1/8 jack with a 1/4 jack. I am using a carbon microphone from a rotary phone. i've tried using the exact box created here and i have also wired the speaker directly into the circuit bypassing the need for the phone chord and i am still unable to get any sound from the mic. i am completely new at this and i have not wired the capacitor or the potentiometer into the circuit. is that the reason why i am not getting any sound? and if that is not the reason does anyone have any idea how i can get this to work? any help would be greatly appreciated. this mic would be amazing for my band's live show. thanks!

try my 'bang it on the floor trick" above if the carbon mic doesn't work...

randofo (author)cimz2008-02-17

I have not installed the capacitor in any of the versions that I have made, but I have added it based on some of the feedback that I have gotten and it is probably a good idea to have it. The potentiometer is needed and that may very well be your problem. My original version didn't use a potentiometer, but had a 100K resistor instead. I added the pot to give a little more control over the fine tuning. Then again, I've built one without any resistors or capacitors at all, but it didn't work on all amps since the signal was kind of high. Maybe you just wired it backwards or you have a bad connection somewhere, perhaps? However, I would try adding a 100K resistor in place of the pot and seeing what happens. Just having a 33K resistor might be confusing the device.

cimz (author)randofo2008-02-17

thanks so much i'll give it a shot

randofo (author)cimz2008-02-18

No problem. Let me know how it goes..

cimz (author)randofo2008-02-19

yep wired it up no problem with the 33k and 100k resistors and it works fine. i am getting a little feedback but its probably in my connections some where. thanks again.

randofo (author)cimz2008-02-19

No problem. I kinda figured that was your problem. It probably just wasn't grounded right.

randofo (author)2008-03-21

This sends out line level audio. You just need to figure out how to send line level audio into the phone.

Jawad_hussain (author)2008-02-21

Your discussion is really helpful and informative keep up the good work

splatterpaintballer (author)2008-02-08

same here. I have no idea

splatterpaintballer (author)2008-02-08

awesome. I'll definetly use the one I made for my rock band. If you want to check out info on my band go to:
<a href="">Visit My Website</a>

cardboarddude (author)2008-01-29

well i finally decied to make one,so i did, but it doesnt work . the wiring looks the same as the one in the pictures . y wont it work?

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Bio: My name is Randy and I founded the Instructables Design Studio. I'm also the author of the books 'Simple Bots,' and '62 Projects to ... More »
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