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Carl Poersch
Carl Poersch, Computer Network Engineer
Category: Computer
Satisfied Customers: 1017
Experience:  Microsoft Certified Systems Engineer, USA, 15+ yrs exp. in PC & Server Hardware, Software, Networks
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When I plug my microphone into the audio jack, it does not

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When I plug my microphone into the audio jack, it does not work and it does not disable the internal microphone. Thinkpad t400, Vista business

I looked a lot on this and likely found your answer. It uses a non-standard microphone plug. Its a technical answer, you will need to take a look at this link.

Your particular thinkpad DOES use a combined mic/line input...

The excerpt is below, but look a the link.

Best of Success!



When attaching an external microphone to the ThinkPad, it does not work. If the connector is removed part way out, then it appears to work.

Affected configuration
Any ThinkPad where one is attaching an external microphone to use instead of the built in microphone .
NOTE: Not all models have built in microphones. Refer to your User's Guide for your particular ThinkPad.

If you are using a condensor microphone, then it must provide own power, either through the use of batteries inside of the microphone, or through the use of an AC adapter. Pulling the connector part way out, the external microphone is no longer disabling the internal microphone which gives the appearance of the external microphone working.

Additional information
Following is an explanation of the ThinkPad microphone connector:

1. Some ThinkPads use a combined microphone or line input connector. Basically, the microphone jack is a 1/8" (3.5mm) stereo mini-jack, but differs from "standard" jacks in two ways:

a. There is a second contact that touches the ground ring when a microphone is connected. The purpose of the second contact is to ground out the internal microphone when an external microphone is plugged. This second contact should be of no consequence for external microphones and their connectors.

b. There is a metal ring on the outside of the connector (visible from outside the ThinkPad). This connects to +5V through a 2.7 kOhm resistor.
Customer: replied 8 years ago.

So ... in non-technical words, I need to replace my headset & any other accessories that used to plug into the microphone jack with my old Thinkpad with accessories that use a "3.5 mm stereo mini-jack" ?

Is that mini-jack compatible with "standard" input connectors?


I know this stuff and A/V pretty well and I found it confusing, Lol...

What I got from the article is that you cant expect to use a regular microphone and have it work and disable the internal mic.

Personally I would go to radio shack, take my current mic, laptop, and a printout of the article, and try a few mic's until you find one that works correctly. Even if you dont want to buy thiers, at least you can find which kind of plug works correctly.

Sound like a good plan??

Customer: replied 8 years ago.

You'd think Lenovo could include a photo of the "standard" and "new".

I'm looking at 3.5 mm jacks thinking that 3.5 mm is the magic feature, and they'are ALL 3.5 mm.

Will go with your Radio Shack idea. Mission for the weekend.

What is the protocol for reconnecting with you later to follow up?

yeah, its pattern on the length. they are all 3.5mm width.

use this link to revisit the question

Did you make any more progress on this issue?

Let me know if you need anything more....


Carl Poersch and 5 other Computer Specialists are ready to help you
Customer: replied 8 years ago.

Carl, the 3-ring 3.5mm plug may or may not be the answer.

I am having trouble sourcing a microphone that uses such a plug. The only ones available are for Blackberry, iPhone etc. and it's not clear whether they are compatible with a PC. I bought a Blackberry mike, but it doesn't work. There may be something Blackberry-specific, so I am going to see if there is a generic cellphone mike and test with that.

I'm beginning to suspect that Lenovo has built the T400 using the combined mike/line-in component to save space, but there are no readily-available consumer products that are compatible. One online store that sells cables refers to their stock of 3-ring 3.5 mm cables as "hard to get".

So at this point, the problem is NOT solved in the sense that the external mike still does not work. And if I do manage to buy a plain old microphone for PC with a 3-ring plug, it still may not work due to Vista or Lenovo settings.

However, in all fairness, your answer is correct in that this T400 requires a mike with a 3-ring plug. Even if such an accessory does not exist for PCs. So I'll accept your answer.

Thanks for accepting. I did do a lot of research and basically answered your question, but didnt solve the problem.

Since it is a relatively new PC, I would go ahead and call Lenovo just on the long shot that they have some article that they didnt publish or a suggestion regarding microphones.

Best of success!