Hello

I encounter the following problem:

phone1--pbx----(fxs)c2610----3640(fxs)---PBX---phone2

I use phone1 to dial phone2,when the callee (phone2) answers the call as soon as he hears the first ring bell.He can not head the words I speak in the frist few seconds(two or three second ).But I can hear the callee voice from the start.After these two or three seconds,the voice is normal .I do not understand why this problem took place?There is any parameaters to controll this problem?