You need to issue the required modem "AT" commands which are "ATM1" and "ATL2" for "sound on until carrier" and "loud volume" respectively.
If you use "pppconfig" - then the folder /etc/chatscripts is a good place to start. There should be an example script called "pap" which shows some "AT" commands being issued.
"ATDT" is the dial command. The phone number string is appended to it. So a phone number of "123456" would become "ATDT123456".
You could - add your commands to this script - by changing the ATDT command to be "ATM1L2DT".
"pon" and "poff" are more "sort of" diagnostic tools. Have a look at
http://www.debian.org/doc/manuals/de...ppp_connection 5.4.3. The PPP connection with pppconfig
Dave