47 CFR § 9.7
Obligation for providing an intercept message
February 16, 2021
Upon termination of permissive dialing, as provided under §9.6, telecommunications carriers shall provide a standard intercept message announcement that interrupts calls placed to the emergency service provider using either a seven-or ten-digit emergency number or an abbreviated dialing code other than 911 and informs the caller of the dialing code change.