My phone doesn't recognize a disconection


I connect a phone (n°1) to my Asterisk with a Sipura interface.
I call this phone (n°1) with an other phone (n°2), I can do a communication beetween the both phones.

But, when I disconect the phone n°2, the phone n°1 ring again and it doesn’t recognize the disconection.

Can you help me?