" e - Perform echo cancelation on this channel.\n"
" Takes mISDN pipeline option as optarg.\n"
" s - Send Non Inband DTMF as inband.\n"
+ " r - re-buffer packets (160 bytes). Required for some SIP-phones and fax applications.\n"
" vr - rxgain control\n"
" vt - txgain control\n"
" Volume changes at factor 2 ^ optarg.\n"