need help on sound recording using bplay

[Long Wind <longwind2009@gmail.com>]

I want to record sound from line-in of sound card,
I enter sth. like:

brec -d /dev/dsp -b 8 -t 15 -w  t2.wav

after that l use bplay to play t2.wav, I can't hear sound

I'm afraid I need to specify line-in, in addition to /dev/dsp, but how to do it?

Thanks!