Is it permissible to interrupt a Fard prayer upon hearing the doorbell or telephone, and how is this interruption performed?

It is forbidden for a worshipper to interrupt an obligatory prayer except out of necessity, such as saving a life from harm or preserving property from loss. Answering the phone or opening the door are not considered necessities. A worshipper may interrupt the prayer by saying the Taslim or by leaving in cases of necessity.