Special prefix codes are limited to Nortel PBX platform. This is the key system forum. With that said, I would be printing dn '7' and '77' to get a clearer picture. Very possibly someone changed AC1 from the usual '9' to get away from false 911 calls. If that comes up empty, I would look at the default codes (how could anyone remember them all?) and the Flexible Feature Codes as well.