Problem with chan_dahdi.conf in spain

I’m running Asterisk along Dahdi, I’ve got a Digium board with 3 FXO ports and 1 FXS port (TDM400P). When we make calls sometimes (this seems to happen randomly) they just end abruptly. We’ve already touched busycount, answerpolarityswitch and hanguponpolarityswitch. The system is running in Barcelona, Spain, could somebody provide me with a working configuration for /etc/asterisk/chan_dahdi.conf? Thanks in advance