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As @kidphc noted, it is the ID of the repeater (more accurately, the GMRS callsign of the owner/operator of the repeater). The FCC does not require that a repeater ID. But, if the repeater does ID, it may do so using morse code or voice. There is no limitation on the allowable speed of the morse code ID, and some repeaters ID at a rate that would challenge the best morse operators out there. This is defined in 47 CFR § 95.1751 - GMRS station identification. You can also search the forum topics onMyGMRS for several lengthly discussions on the subject.