Not sure about the PAP2, but the Linksys 2102 (the Sipura sibling of the PAP2) has a couple of timers in regional settings called "Inter-digit short timer" and "Inter-digit long timer". The one you need to change is the short timer. This controls how long the unit will wait after a digit has been pressed before it assumes that you have completed your dial. The long timer controls how long the unit will wait without any digits being pressed before it gives back a fast busy.
Kind Regards
S