A point in time at which the quantity of TNs within existing CO codes (NXX) which are "Available for Assignment" equals zero within a switching entity/Point Of Interconnection (POI) or, conversely, when the quantities of "TNs Unavailable for Assignment" equal 10,000 times the quantity of existing CO codes (NXX) assigned to a switching entity/POI. Where CO code sharing occurs or partial CO codes are assigned to a switching entity/POI, the latter number should be adjusted accordingly.