Hunt Groups

Every customer wants the best possible phone service at the lowest possible price. They want their customers to be able to get through on the phone lines, but they don't want to pay for more trunks than they need.

One way to make the most efficient use of trunks is by using a feature called hunting. It's the way the network finds available incoming trunks to complete incoming calls. When a trunk is busy with a call, it's not available for other calls. Hunting allows the network to forward an incoming call to the first available trunk.  The CO Switch hunts for the first available trunk. If all trunks in the hunt group are in use, the caller gets a busy signal.

Route Advance

Route advance is a SS7 feature that allows you to hunt across more than one hunt group. Route advance is available only for DID trunks.

Types of Hunting

Series Completion Hunting - each trunk has it's own phone number, but only one of them is a published number.  The sequence, which does not have to be provisioned in numerical order - begins with the published phone number.  When a caller dials the published number, the CO Switch hunts the numbers in sequence until it finds a free trunk.  Sometimes all the trunks in the hunt group are in use. If this happens, the caller gets a busy signal.

Circular Hunting - Sometimes people dial numbers in the middle of a hunt group. That's fine if the trunk associated with that number is available, but what if it is in use? With circular hunting, the CO switch starts with the dialed number in the hunt group. It hunts from that point to the end of the sequence, then continues to hunt from the beginning of the sequence. Circular hunting does not continue around the loop until a trunk becomes available. If all the trunks in a hunt group are in use, the switch makes just one sweep around the loop, then sends the caller a busy signal.

Multiline Hunting - this method allows all the trunks to share a single published phone number.  In addition to the number, each trunk always has its own terminal number (usually in addition to a phone number) to define the hunt sequence. In this example, all the trunks have the same phone number - 555-1000 - but have different terminal numbers TER1, TER2, etc. Assigning terminal numbers lets you use a single published phone number.  When a caller dials the published number, the CO switch hunts the number in sequence by terminal number (rather than by phone number, as with Series Completion hunting) until it finds a free trunk.  If all the trunks in the hunt group are in use, the caller gets a busy signal.