Typically, a Trunk is a communication path between central office switches, or between the 9-1-1 Control Office and the PSAP.
Trunk Alternate Route
The routing condition that occurs when all trunks from the end office to SR (Selective Router) are out of service. The scenario represents an end office to SR trunk failure condition versus an all trunks busy condition.
One or more trunks terminated at the same two points.
The point in time at which a 9-1-1 call is assigned to a trunk and acknowledgment is provided by the equipment at the distant end.