Sec.  90.243   Mobile relay stations.

   (a) Mobile relay operations will be authorized on frequencies below 512 MHz,
   except in the Radiolocation Service.

   (b) Special provisions for mobile relay operations:

   (1) In the Public Safety Pool, medical services systems in the 150–160 MHz
   band  are permitted to be cross-banded for mobile and central stations
   operations with mobile relay stations authorized to operate in the 450–470
   MHz band.

   (2) [Reserved]

   (3) In the Industrial/Business Pool, on frequencies designated with an
   “LR” in the coordinator column of the frequency table in  Sec. 90.35(b)(3),
   mobile relay operation shall be on a secondary basis to other co-channel
   operations.

   (4) Except where specifically precluded, a mobile relay station may be
   authorized to operate on any frequency available for assignment to base
   stations.

   (5) A mobile station associated with mobile relay station(s) may not be
   authorized to operate on a frequency below 25 MHz.

   (c) Technical requirements for mobile relay stations.

   (1) Each new mobile relay station with an output power of more than one
   watt, and authorized after January 1, 1972, that is activated by signals
   below 50 MHz shall deactivate the station upon cessation of reception of the
   activating continuous coded tone signal. Licensees may utilize a combination
   of digital selection and continuous coded tone control where required to
   insure selection of only the desired mobile relay station.

   (2) Mobile relay stations controlled by signals above 50 MHz or authorized
   prior  to January 1, 1972, to operate below 50 MHz are not required to
   incorporate coded signal or tone control devices unless the transmitters are
   consistently activated by undesired signals and cause harmful interference
   to  other licensees. If activation by undesired signals causes harmful
   interference, the Commission will require the installation of tone control
   equipment within 90 days of a notice to the licensee.

   (3) Except in the Industrial/Business Pool, on frequencies designated with
   an “LR” in the coordinator column of the frequency table in  Sec. 90.35(b)(3),
   each new mobile-relay station authorized after January 1, 1972, shall be
   equipped for automatic deactivation of the transmitter within 5 seconds
   after the signals controlling the station cease.

   (4) Except in the Industrial/Business Pool, on frequencies designated with
   an “LR” in the coordinator column of the frequency table in  Sec. 90.35(b)(3),
   each new mobile-relay station authorized after January 1, 1972, during
   periods that is not controlled from a manned fixed control point; shall have
   an automatic time delay or clock device that will deactivate the station not
   more than 3 minutes after its activation by a mobile unit.

   (5) In the Industrial/Business Pool, on frequencies designated with an
   “LR” in the coordinator column of the frequency table in  Sec. 90.35(b)(3), each
   mobile relay station, regardless of the frequency or frequencies of the
   signal by which it is activated shall be so designated and installed that it
   will be deactivated automatically when its associated receiver or receivers
   are not receiving a signal on the frequency or frequencies which normally
   activate it.

   (6) Multiple mobile relay station radio systems shall use wireline or radio
   stations  on fixed frequencies for any necessary interconnect circuits
   between the mobile relay stations.

   [ 43 FR 54791 , Nov. 22, 1978, as amended at  49 FR 40177 , Oct. 15, 1984;  50 FR 13606 , Apr. 5, 1985;  50 FR 39680 , Sept. 30, 1985;  50 FR 40976 , Oct. 8, 1985;
    54 FR 39740 , Sept. 28, 1989;  56 FR 19603 , Apr. 29, 1991;  56 FR 32517 , July
   17, 1991;  60 FR 37268 , July 19, 1995;  61 FR 6576 , Feb. 21, 1996;  62 FR 18928 , Apr. 17, 1997]