[Freeswitch-users] Default maximum number of simultaneous outgoing PSTN calls

Hi, I am making simultaneous outgoing calls to PSTN network through freeTDM and PRI card via Event socket. FS only generates at max. four calls and for the rest it shows NORMAL_CIRCUIT_CONGESTION. What could be the possible reason for this? Is there any default maximum limit on the number of simultaneous outgoing calls through freeTDM/libpri/DAHDI stack.? Kindly throw some light on this. Regards. -- Ashish