Goto Section: 90.239 | 90.242 | Table of Contents
Revised as of October 20, 2020
Goto Year:2020 |
§ 90.241 Radio call box operations.
(a) The frequencies in the 72-76 MHz band listed in § 90.257(a)(1) may
be assigned in the Public Safety Pool for operation of radio call boxes
to be used by the public to request fire, police, ambulance, road
service, and other emergency assistance, subject to the following
conditions and limitations:
(1) Maximum transmitter power will be either 2.5 watts plate input to
the final stage or 1 watt output.
(2) Antenna gain shall not exceed zero dBd (referred to a half-wave
dipole) in any horizontal direction.
(3) Only vertical polarization of antennas shall be permitted.
(4) The antenna and its supporting structure must not exceed 6.1 m (20
feet) in height above the ground.
(5) Only A1D, A2D, F1D, F2D, G1D, or G2D emission shall be authorized.
(6) The transmitter frequency tolerance shall be 0.005 percent.
(7) Except for test purposes, each transmission must be limited to a
maximum of two seconds and shall not be automatically repeated more
than two times at spaced intervals within the following 30 seconds.
Thereafter, the authorized cycle may not be reactivated for one minute.
(8) All transmitters installed after December 10, 1970, shall be
furnished with an automatic means to deactivate the transmitter in the
event the carrier remains on for a period in excess of three minutes.
The automatic cutoff system must be designed so the transmitter can be
only manually reactivated.
(9) Frequency selection must be made with regard to reception of
television stations on channels 4 (66-72 MHz) and 5 (76-82 MHz) and
should maintain the greatest possible frequency separation from either
or both of these channels, if they are assigned in the area.
(c) Frequencies in the 450-470 MHz band which are designated as
available for assignment to central control stations and radio call box
installations in § 90.20(c) or § 90.20(d)(58) may be assigned in the
Public Safety Pool for highway call box systems subject to the
(1) Call box transmitters shall be installed only on limited access
highways and may communicate only with central control stations of the
(2) Maximum transmitter power for call boxes will be either 2.5 watts
input to the final amplifier stage or one watt output. The central
control station shall not exceed 25 watts effective radiated power
(3) The height of a call box antenna may not exceed 6.1 meters (20
feet) above the ground, the natural formation, or the existing man-made
structure (other than an antenna supporting structure) on which it is
mounted. A central station transmitting antenna, together with its
supporting structure shall not exceed 15 m. (50 ft.) above the ground
(4) Only F1D, F2D, F3E, G1D, G2D, or G3E, emission may be authorized
for nonvoice signaling, radiotelephony, and multiplexed voice and
nonvoice use. The provisions in this part applicable to the use of F3E
or G3E emission are also applicable to the use of F1D, F2D, G1D or G2D
emission for call box transmitters.
(5) The station identification required by § 90.425 shall be by voice
and may be transmitted for the system from the central control station.
Means shall be provided at each central control station location to
automatically indicate the call box unit identifier when a call box
unit is activated.
(6) Call box installations must be so designed that their unit
identifier is automatically transmitted when the handset is lifted.
(7) Each application for a call box system must contain information on
the nonvoice transmitting equipment, including the character structure,
bit rate, modulating tone frequencies, identification codes, and the
method of modulation (i.e., frequency shift, tone shift, or tone phase
(8) Call box installations may be used secondarily for the transmission
of information from roadside sensors. Central control station
transmitters may be used secondarily to interrogate call box roadside
sensors and for the transmission of signals to activate roadside signs.
(9) Each call box transmitter must be provided with a timer which will
automatically deactivate the transmitter after 2 minutes unless the
central control station operator reactivates the timer cycle.
(10) The central control station must include facilities that permit
direct control of any call box in the system.
(11) Call box transmitter frequency tolerance shall be 0.001 percent.
(12) Transmitters certificated under this part for use of F3E or G3E
emission may be used for F1D, F2B, G2B or G2D emission provided that
the audio tones or digital data bits are passed through the low pass
audio filter required to be provided in the transmitter for F3E or G3E
emission. The transmitter must be adjusted and operated so that the
instantaneous frequency deviation does not exceed the maximum value
allowed for F3E or G3E emission.
(d) In addition to the frequencies available pursuant to § 90.20(c) the
frequencies set forth in § 90.20(d)(58) may be used for central control
station and call box installations in areas where such frequencies are
available for fixed system use subject to the requirements and
limitations of that section and subject to the provisions of paragraphs
(c) (1), (4), (5), (6), (7), (8), (9), (10), and (12) of this section.
[ 43 FR 54791 , Nov. 22, 1978; 44 FR 32219 , June 5, 1979; 49 FR 48712 ,
Dec. 14, 1984; 50 FR 39680 , Sept. 30, 1985; 50 FR 40976 , Oct. 8, 1985;
54 FR 38681 , Sept. 20, 1989; 54 FR 45891 , Oct. 31, 1989; 58 FR 44957 ,
Aug. 25, 1993; 62 FR 18927 , Apr. 17, 1997; 63 FR 36610 , July 7, 1998;
63 FR 68965 , Dec. 14, 1998; 72 FR 35195 , June 27, 2007; 78 FR 25175 ,
Apr. 29, 2013]
Goto Section: 90.239 | 90.242
Goto Year: 2020 |
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