How does the microphone jack know that a microphone is plugged in?

There's an electro-mechanical 'sensor' -- normally there's a little switch (or a pair of them for a stereo jack) that are normally closed, but get pushed open when a headset is plugged in. Normal practice is to just wire the sound through the jack, to the speaker.

I keep saying 'normal' here because if your device is actually _indicating_ that there's something plugged in, then they're doing something more sophisticated than just switching the audio after all else is said and done. If this is, indeed, the case, then something else could be broken.

Try replacing the jack, see if it helps.

Actually it's 3.5 mm !

Graham

So all this switch does is to open the circuit? What's the point in that? Without the headset plugged in, isn't the circuit already closed?

It opens the circuit to the speakers, or sometimes it opens the circuit between the drive amplifier and the final, so that with headphones you just get the output of the drive amp.

Sorry, I still don't understand. There are only three cables going to the jack from the device: ground, left channel, right channel. Without the headset plugged in, how can any circuit be open, even without a switch?

If you know there are only three traces connecting to the jack inside the device, then it's most likely measuring the impedance of whatever you plug in, to try to guess what it is.

Only where it doesn't matter.

Is that why those crappy jacks don't make contact half of the time?

The original 1/8" plugs and jacks were very good quality, but the imported crap is just that. I have Switchcraft 1/8" connectors that are almost 40 years old, and still work like the day I bought them.

thinks

presume

jack

Can

How does your device indicate the headset is connected ? is there a LED or a lcd display indicator ?

anyways in the simplest method... the headset jack is a set of contacts installed in series with the output lines to some external output like speaker out. inserting a headset plug into the headset jack simply moves the contacts apart and the plug intercepts/redirects the output signal to the headset.

Removing the plug allows the contacts to spring back into their series connection and the signal is no longer intercepted and will continue on to the external output.

if one of those contacts breaks or is blocked by some scata/crud/gunk then the jack will not be able to reset itself into a series connection and the signal stops at the headset jack.

that is the mechanical method. hth robb

wait a minute, what are we talking about here? first you said headphone/microphone jack, now it's left channel and right channel?

How does your device think the earphones are plugged in? I presume your main speakers aren't working.

The "normal" wiring is for the wires for the speakers to go via the earphone jack. The earphone plug has terminals which open when the earphone plug is inserted thus cutting off supply to the speakers.

These contacts may be bent so that when you remove the earphone plug they stay open.