Speak your mind

  • Fancy the idea of anonymous free speech in public places? This inventor thought it would be a great idea to create a sort of mobile
  • Your cellphone offers huge possibilities with just a paper cone, a battery and a few bits of wire
Date:31 March 2006 Tags:

You have the right to make yourself heard, says Daniel Jolliffe. Here’s how he did it…

IF you’re walking through your local park and happen upon a device looking like something out of , with loud random voices blaring from it, you’ve found Daniel Jolliffe’s “One Free Minute”.

Designed to promote anonymous public speech, One Free Minute allows calls to the cellphone inside the sculpture to be connected for exactly one minute to a 200-watt amplifier and speaker. The results can be empowering, funny, touching – and downright loud. The speech produced by Jolliffe’s sculpture can be heard clearly for more than 45 metres.

The 41-year-old Canadian artist created this compelling machine for his master’s thesis project at Ohio State University. It’s attached to a bicycle for easy movement, and he’s taking it on tour throughout the US and Canada.

There’s clearly a political aspect to One Free Minute. By creating a tool that allows anonymous free speech in public places, Jolliffe hopes to let activists speak without fear or recrimination at a time when governments everywhere are increasingly vigilant of who is saying what and where.

The sculpture was designed in Rhino CAD, which offers a wide range of visualisation options. Once Jolliffe settled on the look he wanted, he used a process similar to building a wooden boat, creating the shell out of glass fibre and epoxy, and then sanding – lots of sanding. The electronics turned out to be the easy part. Jolliffe assembled the embedded controller by hand, threw in an off-the-shelf car stereo amplifier, a couple of gel cell batteries, a 200-watt compression driver, and a serially controlled MP3 player. The sculpture was ready to make some serious noise.

From the woman who called to say she had pancreatic cancer and wanted to tell her children she loved them before she died, to political ranters, to silly singers, Jolliffe credits them all. “The people who call up and lay their guts on the line, saying what they really think – this piece was built for them and they are the real creators of what is good about One Free Minute.” –

Throw your voice!
You, too, can bring anonymous voices into public spaces, stage an anonymous protest, or speak to the masses without revealing your identity. I’ve created a grander version of this anonymous megaphone (see picture), but a cellphone, some construction paper, a battery and a few wires can easily do the trick.

Turning your cellphone into an automatic megaphone is a snap. I’ll show you how to build an unattended megaphone that projects a caller’s voice up to 10 m – it all depends on how big a horn you make. It should take about two hours to put together, assuming some familiarity with soldering and basic electronics, and cost you no more than R70. Once you get all the parts together, there are basically just two simple steps on the road to anonymous oration.

Solder it


  • 9-volt battery and clip
  • Small perf board
  • Headset plug for cellphone, with wire attached
  • Three capacitors, rated for 16V or more: 100-300 μF, 22-33 μF, and 1 μF
  • 1-10 KΩ resistor
  • Diode, any from 1N4001-1N4004 series
  • 10 KΩ trim-pot
  • 7-16 Ω speaker, about 4 cm in diameter (use a transistor radio-type speaker, not something out of a pair of headphones)
  • Amplifier chip, prefer LM386N-3 or N-4, but LM386N-1 will work
  • Tie-wraps, hot glue, sturdy cardboard for megaphone, about 60 x 90 cm

1. Cut the perf board to size and solder the LM386 in the middle.
2. Drill a hole to the end of the board, to tie-wrap the battery and headset cable.
3. Solder the battery clip and headset wires. With a cable from a cheap headset, you’ll have to heat the wire until the enamel covering the wire melts. Tie-wrap them to the board.
4. Identify the headset cable connections. The plug’s sleeve goes to ground, the ring is the phone’s speaker, and the tip is its microphone.
5. Connect a 1-10 KΩ resistor between the tip wire and ground. This fools your cellphone into thinking that a headset is connected. You may have to experiment with different values (I used 2,2 KΩ).
6. Solder in the rest of the capacitors and the volume control – see the diagram above. Attach the speaker with about 15 cm of wire. Don’t forget the blocking diode – this projects your circuit when you inevitably connect the battery clip backwards at 1 am. If you don’t want a volume knob, substitute a resistor of the 10 K pot and control the volume from your phone.

Possible problems
>> The headset cable isn’t soldered in properly. Use a multimeter to check its three connections.
>> Some Nokia phones don’t use a standard headset jack. If that’s the case, get an adapter.
>> Most of the component values in this circuit can be approximate, but the one crucial part is the resistor from the tip of the headset plug to ground, which fools the cell into thinking a headset is connected. You may have to swap resistors to tweak this value, depending on your cellphone model.
>> If you get feedback and oscillation, you may have to add a suppressor: solder a 0,05μF capacitor in series with a 10Ω resistor from pin 5 to ground. Another option is to reduce the pin 1-8 capacitor to 22 μF (or even 10 μF), which lowers the gain of the amplifier.

Assemble it
Roll up the card stock into a cone shape and hot glue the seams to hold it together. Cut the end of the paper horn to fit the speaker, and hot glue it on. (Hot glue is just terrific, isn’t it?) Now hot glue or Velcro the battery and amplifier to the horn. Set your phone to auto-answer after a few rings. Make sure it’s also set to route audio through the headphone jack. Velcro your cellphone to the horn. Congratulations – you’ve created an anonymous public speech device.

Reproduced with the kind permission of MAKE magazine () and Daniel Jolliffe.


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