Authorization codes prevent unauthorized access to some system facilities. When a user dials an authorization code, the system checks the code. If the code is invalid, the system generates the intercept tone. If the code is valid, the system uses the COR and the FRL that is associated with the authorization code for further call processing. However, if AFRL is activated, the system uses the AFRL for further call processing.

If the system uses an intertandem tie trunk group for a call, the system outpulses a TCM as the last digit of the number. If the FRL of the intertandem tie-trunk is equal to or greater than the terminating FRL, the system proceeds with call processing. If the FRL of the originator is less than the FRL of the termination point, the system compares the TCM with the FRL of the tie trunk. If the TCM is greater than or equal to the FRL of the tie trunk, the system proceeds with call processing.