Sec.  90.475   Operation of internal transmitter control systems in specially
equipped systems.

   (a) An internal transmitter control system need not be designed to meet the
   requirements of  Sec. 90.473 if it meets the following requirements:

   (1) All operating positions must be located on premises controlled by the
   licensee.

   (2) An internal transmitter control system may be used in conjunction with
   other approved methods of transmitter control and interconnection so long as
   the internal transmitter control system, itself, is neither accessed from
   telephone positions in the public switched telephone network (PSTN), nor
   uses dial-up circuits in the PSTN. Licensees with complex communications
   systems involving fixed systems whose base stations are controlled by such
   systems may automatically access these base stations through the microwave
   or operational fixed systems from positions in the PSTN, so long as the base
   stations and mobile units meet the requirements of  Sec. 90.483 and if a separate
   circuit  is  provided  for each mode of transmitter operation ( i.e. ,
   conventional, dial-up or Internet).

   (3) The system must be designed so that upon completion of a transmission,
   the base station transmitter(s) will close down automatically within 3
   seconds.

   (4) To guard against malfunctions, the system must also be designed so that
   the base station(s) will be deactivated by an automatic timing device when a
   modulated signal is not transmitted for a period of three (3) consecutive
   minutes.

   (5) The system must include automatic monitoring equipment, installed at the
   base station transmitter site(s), which will prevent the activation of the
   system when signals of other co-channel stations are present.

   (b) [Reserved]

   [ 43 FR 54791 , Nov. 22, 1978, as amended at  44 FR 67125 , Nov. 23, 1979;  47 FR 17521 , Apr. 23, 1982;  72 FR 35199 , June 27, 2007]

Interconnected Systems