47 CFR 95.21 - GMRS system description.
A GMRS system is one or more transmitting units used by station operators to communicate messages. A GMRS system is comprised of:
(a) One or more station operators;
(b) One mobile station consisting of one or more mobile units (see § 95.23 of this part);
(c) One or more land stations (optional);
(d) Paging receivers (optional); and
(e) Fixed stations (optional).