Method and apparatus for routing blocked telephone calls

摘要

A telecommunication system includes a private branch exchange (17O) that uses an automatic route selection algorithm to select a trunk on which a call is to be routed. A number of trunk groups are queried for an available trunk and once an available trunk is located, the call is placed. The automatic route selection algorithm monitors the call to determine if an error message or error tone is received. If an error message or error tone is received, a set of remaining trunk groups not previously queried are queried for an available trunk to route the call. <IMAGE>