I just wanted to let my fellow free operating system enthusiasts know this.
If you have an old pair of 1/8 inch jack headphones, you can plug them into the slot reserved for microphones, and this will work in a pinch for use as a microphone. An old friend showed me this trick when we were using Skype as an instant messenger. I believe but cannot be sure that the left side of the headphones will act as a microphone- a good condenser mic which will pick up voice and music fairly well.
This is how it works. The speaker of the headphone has a magnet and a small speaker cone. The microphone jack recieves power exactly the same way and sends the signal from the magnet to the sound card.
No this is not a studio quality sound, but VOIP calls such as Ekiga, and Skype will be heard very well. If your microphone is broken, or you don't want to spend 20-30 bucks, this will work. The clarity is good enough and won't hurt your computer either.

I do not recommend it because the microphone jack uses phantom power or a power source to make the pre-amplifier in condenser microphones work. A condenser microphone compared to a headphone speaker is different. One is capacitor based and the other one is dynamic or a magnet and a coil. The phantom power will travel from one of the headphone and ground. The coil in one of the speakers will become hot and you can damage the phantom power circuitry.

All dynamic speakers can be microphones. Lighter the cone and softer the suspension, better the speaker driver is as being a microphone.

Well I didn't know that. It hasn't fried on me yet, but maybe I should give it a break and just use a real microphone. Thanks

Many devices are reversible, but are not necessarily the best choice when used in reverse.

My favorite is the induction motor. If you spin it, it will not generate power. If, however, you first connect it to the power line and then force it above the synchronous speed (eg with another motor), it will push power into the grid.

Do not try this at home.....

Internal combustion engines and most types of heating and cooling appliances are NOT reversible.

Headphones are good microphones in the days when outputs were outputs and inputs were inputs. I have used this for years when microphone inputs had 6.3mm jack, just like headphones.

However, modern PC microphone outputs have a so called phantom power supply wich provides a voltages for today's (capacitor?) microphones.

I discovered this after blowing up 4 conventional microphones, they all lasted one or two days.

jlinkels

Phantom power +48V is not quite the same as a bias voltage / plug-in power +5V. I've used a pair of headphones as a mic for a while. It only works because of the voltage (otherwise you need a battery box). It does not work with all soundcards, mainly the cheapo laptop variety. The newer high definition ones seem to lack the voltage. And the voltage generally means a high noise floor (hiss). And most times it only works for NON full duplex soundcards. Which doesn't work well for things like skype as the output signal has a built in feedback to the input channel of sorts. But useful for that cheesy sort of store PA sound system type effect.

Any voltage used to supply an element on the line, not interfering with the signal to be carried, is called a phantom power. Being it -48 V (in telephony it is minus), +90V for ISDN, +24V, +12V for antenna amplifiers, +5V for microphones.

That is new for me, a dynamic headphone needing a DC power supply to work? A headphone element is a generator. It would work despite of the DC voltage, not because of it. Unless you had a very special electret type.

jlinkels