8 ms·
Here's a neat party trick for you. I had a MacGyver moment in the past where I made a phone call with only are pair of old earbuds and a phone cord (no switche
by bcheung 10y ago
Here's a neat party trick for you.
I had a MacGyver moment in the past where I made a phone call with only are pair of old earbuds and a phone cord (no switches, no dial pad).
A speaker is basically the same thing as a microphone in reverse. Normally it takes an electrical signal to move a physical element that creates the sound waves. But you can also move the element and it will generate an electrical signal.
To dial you can use the old rotary trick. The old phones dialed by pulses of quickly disconnecting and reconnecting. You can do that by hand if you want but it might require a little bit of practice and dexterity. Basically if you want to dial a 5, just disconnect the wire from the headphone to the phone cord and then reconnect it 5 times in a row.
You have to both listen and speak through the ear bud. Not the best quality or easiest to do but it works.
- enraged_camel 10y agoI don't know what kinds of parties you attend, man... But that sounds like a fun trick!
- anigbrowl 10y agoYou don't even need to disconnect the ear bud, just tap it. The voltage pulse from an audio signal is sufficient. Back in the days of rotary phones I used to show off how to dial numbers by simply tapping the receiver on the table.
- Johnny555 10y agoThat doesn't seem to work - I have a POTS line here, and no amount of tapping or striking the phone receiver on a surface is the equivalent of dialing (I tried the phone itself and my headset microphone). Perhaps a local VoIP ATA works that way, but my Telco does not. And I'm not surprised, there's a big difference between detecting an audio signal and detecting a local loop interruption through 18,000 feet of copper.
- qb45 10y agoI'm under impression that pulse dialing had been phased out in many countries, with tone dialing being the replacement.
- Johnny555 10y agoPerhaps so in some countries, but in the USA, pulse dialing still works (even VoIP ATA's here support it). There's lots of older automated equipment out there that depends on it (elevator call boxes, alarm systems, building front door call boxes, etc.) My "in case of power failure" phone is an old red Bell System desk phone with rotary dial. Still works great.
- deleted 10y ago[deleted]
- illumin8 10y agoAs a DJ, I learned the trick to plugging your headphones into the Mic jack and yelling very loudly into the cans as a cheap microphone. It works in a pinch; not the best sound quality though.
- branchless 10y agoWelcome Kevin Mitnick!
- mathiasben 10y agoI've used this before in a pinch too, speaker as a microphone in reverse. that got me wondering... would it be possible to use the same principle with another type of listening device. Focusing a laser beam on a window allows you to hear a conversation in the room. so could the same principle be applied and allow a laser beam to transmit audio?
- JimmyAustin 10y agoI'm not 100% sure of the math involved, but I think any laser that impacts a window enough to vibrate it would probably just melt it instead.
- dom0 10y agoYou can actually make music with a laser cutter.
- toomanybeersies 10y agoYou can use a laser to transmit audio to a LDR or a light sensitive transistor/diode, which can then be used to run a speaker (with a battery attached). Essentially fibre optics through the air. I did it once, the quality was rather lacking, since it used amplitude modulation instead of frequency modulation. Here's an instructable on it: http://www.instructables.com/id/How-to-Send-Sound-using-a-Laser/ http://www.instructables.com/id/How-to-Send-Sound-using-a-La... It's not quite what you're asking, but it's probably the closest you can feasibly get. I'm fairly sure that's also the way that laser microphones work as well.
- mountaineer22 10y agoDid you know you can use a DC motor as a speaker, too? I have not tried using a motor as a mic.
- mikey_p 10y agoGood ole' Servodrive. I've read some threads with Tom Danley on a few message boards and he is one incredibly fascinating individual. Wouldn't the efficiencies between input/output transducers be inverse? A servo drive transducer would use very little energy to produce a lot of acoustic output, so wouldn't it require a large amount of acoustic input to generate any signal at all?
- bigiain 10y agoAC motors as well. Lots of brushless quadcopter motor controllers buzz out diagnostic/startup tones from the motors as they power up.
- telekid 10y agoHow do you dial a zero? Edit: Just realized why a zero is in the '10' position on a rotary phone. Huh.
- ptaipale 10y agoYes, except in the Swedish phones, where the numbering starts from 0. So dialing 0 would make 1 pulse, dialing 1 would make 2 pulses, and dialing 9 would make 10 pulses.
- bigiain 10y agoThat would have confused the guys in The Wire who eventually figured out the bad guys "jump 5" phone number encoding...
- bmm6o 10y agoThe plot point in question was that they were encoding the phone number when leaving it as a callback number. Pulse dialing wouldn't have come into it.
- toomanybeersies 10y agoAnd New Zealand, where it was like Sweden, but backwards. 0 made 10 pulses, 1 made 9 pulses, and dialing 9 would make 1 pulse. This is why the emergency number in NZ is 111, we had equipment from the UK, where the number was 999. As to why it was backwards, I have no idea.
- deleted 10y ago[deleted]
- christoph 10y ago112 still works as an emergency number in the U.K. to this day.
- 10y ago
- amelius 10y agoHow would this trick translate to the modern world of proprietary protocols? Would MacGyver have a fighting chance?