Powerbook microphone problem

I'm testing out a copy of ViaVoice for review, but it refuses to use the internal microphone on my PowerBook (G4, running Panther).

But it won't recognise the microphone that came with it, or any of the two others I've tried plugging in. All three of these (one USB, which I've been using to try out Dragon Naturally Speaking, whose mic it was, the other two the kind with two jacks) fail.

The USB one doesn't work at all (yes, it works on the PC), and the two with separate mic and headphone jacks work on the headphone part but not on the mic part.

The microphone port on the Powerbook isn't marked with the usual mic symbol, and calls itself an "audio line in port". Its definition in the manual says: "Connect your PowerBook to a line-level microphone or other audio equipment".

What's a line-level microphone? Is that something different from the type of mic that humans normally use?

Any ideas for finding out if it's just not working or if there's something I can do to make it work? (Or to force Via Voice to use the internal mic?)

No, the sound isn't muted; it's *showing* a second mic in the system prefs, but Via Voice isn't recognising it.

Is there any way I can test the mic by recording to some other program, to see if it's seen by the Mac generally?

Sorry, I was using the wrong headset and mic. ViaVoice comes with a USB mic with a speaker cable running out from the USB adapter. I had the USB bit plugged in, but not the speaker cable. (The same USB gadget had worked on the PC without the separate cable.)