No UDPTL ports remaining

i used the t38 passthrough model in asterisk 1.2.4.
but when calls are at large, the some warning appears as following

Dec 10 18:14:31 WARNING[5918]: udptl.c:830 ast_udptl_new_with_bindaddr: No UDPTL ports remaining
Dec 10 18:14:31 WARNING[32092]: udptl.c:830 ast_udptl_new_with_bindaddr: No UDPTL ports remaining
Dec 10 18:14:31 WARNING[32095]: udptl.c:830 ast_udptl_new_with_bindaddr: No UDPTL ports remaining

i’ve changed udptl.conf to allowing more port to be used bye UDPTL.but i don’t know how to apply it,just use reload at CLI "CLI> reload "?
i do,but warning still appears.
someboday can give any suggestion ?
Thanks