47 CFR § 95.1751 - GMRS station identification.
Each GMRS station must be identified by transmission of its FCC-assigned call sign at the end of transmissions and at periodic intervals during transmissions except as provided in paragraph (c) of this section. A unit number may be included after the call sign in the identification.
(a) The GMRS station call sign must be transmitted:
(1) Following a single transmission or a series of transmissions; and,
(2) After 15 minutes and at least once every 15 minutes thereafter during a series of transmissions lasting more than 15 minutes.
(b) The call sign must be transmitted using voice in the English language or international Morse code telegraphy using an audible tone.
(2) The GMRS stations whose communications are retransmitted are properly identified in accordance with this section.