With our 911 system and Intrado, we found we have to let our office 911 phone ring 2 times before picking up the receiver to let the mapping kick in. Yes it does ring on the caller side prior to when it rings in the office, but for our data to pick up the mapping we find we let the 911 ring in office 2 times before picking it up. we figured this out when we first were programming towers.
Works for us.
Pierce Co NE