From what I can piece together from the various Mac support forums, a mic-and-headphone headset connected on the audio line in port won't pick up microphone input; the sound card is too cheap, and it needs a preamp. I will have to go with Bluetooth or USB (and I'm not sure what I'll do if I feel like recording some music, but I'll figure that out if the time comes).
(I'm sick of paying $58 a month when my land line phone is increasingly unusable, so I've decided to disconnect it, and stick with Skype when I'm at home and my cell phone otherwise).
(I'm sick of paying $58 a month when my land line phone is increasingly unusable, so I've decided to disconnect it, and stick with Skype when I'm at home and my cell phone otherwise).