23 CAR § 466-1103. Local exchange traffic capability

Local central office equipment shall meet the following minimum requirements during an average busy hour of the busy season: (1) Dial tone delay. (A) A calling party should receive dial tone within three (3) seconds. (B) For the purpose of evaluating the quality of service, the average dial tone delay shall be three (3) seconds or less; and (2) Switching equipment status. (A) A calling party originating traffic that terminates within a central office shall encounter: (i) A ring-back tone; (ii) A busy signal; or (iii) An intercept recording. (B) A calling party originating traffic that is blocked due to insufficient intraoffice trunking shall receive a signal indicating an “equipment busy” condition.