well i bought at headset with mic, and plan to use it when video conferencing. but i plugged my mic jack into the line in port but there is not signal detect. had set to use line in in sound preference instead of bulit in mic. but no luck. so what should i do ? i'm using my mic have no problem since i have a USB that support Audio in and Audio out. but i dont want to use the USB port for video conferencing since i have many USB device need USD port.

From my experience, it's impossible to make it work as 1 aux cable can only work either input OR output...in your case, it will not detect input signal from your mic as your aux cable is working as an output for the headphone...the USB device u have which support audio input and output is the only way that i know which allow input and output for headset with mic...otherwise, u'll have to use the lappie's built in mic for voice input but that will not allow u private conversation as ur speech need to have decent volume and clarity for the Mac's mic to decode ur encoded messages...hope this helps...

well ok as what u said, can't work in pair. so if i just plug in my mic and unplug the headset audiojack in the port will my mic functioning. ermm i tried but no. well so is it means that if i use separate headset and mic might can do that ?

My customer tried those still can't work parallely...it won't serve the headset purpose ad if u separate both item anyway. U might wanna consider sumthin like the iMic from Griffin...but i guess it's similar to the USB device which allow 1 input and 1 output from USB port...

well ok, understand. but one question about this. so what for apple bulit this port for ? how to use it ? according to my googling. said only digital input allowed. well so i put my iPod to this port. yes there is input signal detected showed in the system preference > sounds but when i open garageband and tried to record the signal from my iPod. no luck man. so can i know what for apple bulit that port for ?

I havent try to use that port on MBP or MB...but i often use it on iMac or Mini to record my guitar session like this...

Hope this link give u a better idea what the input is design for...

well so do u mean that apple design the audio line in is just from those instruments input to mac machines ?

you guys sometimes can be blur like sotong.

line in = not for Microphones. its for recording from non-amplified sources.