Thank you for your answer, I think I posted dhadi version and so but let me add more details and recap them below: We are using asterisk 1.8.12.0 with dahdi 2.6.0, on CentOS 6.2. it's a digium card 1HA8-0400BLF output of dahdi_hardware: pci:0000:04:08.0 wctdm24xxp+ d161:8008 HB8-0000