1- I called the VU from internal Extension , and it's working well .
2-configured an extension as a default incomming number and make sure that i can recive calls on this exyension , and i ca hear the DTMF tone.
3-i checked the codec using the following command show mrsparas and i found it ULAW and this is the probem .
4-I changed the codec to be ALAW using this command [config modify mrsparas tdmcodec alaw ] .
5-after changing the codec evry thing is going well.