47 CFR §69.130

1. (a)To the extent that the costs of ISDN line ports, and line ports associated with other services, exceed the costs of a line port used for basic, analog service, non-price cap local exchange carriers may recover the difference through a separate monthly end-user charge, provided that no portion of such excess cost may be recovered through other common line access charges, or through Connect America Fund Broadband Loop Support.
2. (b)The maximum charge a non-price cap local exchange carrier that elects model-based support pursuant to § 54.311 of this chapter or Alaska Plan support pursuant to § 54.306 of this chapter may assess is the rate in effect on the last day of the month preceding the month for which model-based support or Alaska Plan support, as applicable, is first provided.