Sec. 74.939  Special rules governing ITFS response stations.

    (a) An ITFS response station is authorized to provide communication 
by voice and/or data signals with its associated instructional 
television fixed station for use in instructional or computer-assisted 
communications. Other communications concerning the technical operation 
of the system may be carried on when necessary.
    (b) An ITFS response station may be operated only by the licensee of 
an instructional television fixed station and only at an authorized 
receiving location of the instructional television fixed station with 
which it communicates. More than one ITFS response station may be 
operated at the same or different locations by the same licensee. An 
application for authority to operate a new or modified response station 
shall be filed with the Commission in Washington, DC, on FCC Form 330. 
Section VI of that form shall supply the following information for each 
response station:
    (1) The name of the school or other description of the building in 
which the ITFS response station will be located, the address, and the 
geographic coordinates of the ITFS response station transmitting 
antenna.
    (2) The manufacturer's name, type number, operating frequency, and 
power output of the proposed ITFS response station transmitter.
    (3) The type of transmitting antenna, power gain, and azimuthal 
orientation of the major lobe of radiation in degrees measured clockwise 
from True North.
    (4) A sketch giving pertinent details of the ITFS response station 
transmitting antenna installation including ground elevation of the 
transmitter site above mean sea level; overall height above ground, 
including appurtenances, of any ground-mounted tower or mast on which 
the transmitting antenna will be mounted or, if the tower or mast is or 
will be located on an existing building or other manmade structure, the 
separate heights above ground of the building and the tower or mast 
including appurtenances; the location of the tower or mast on the 
building; the location of the transmitting antenna on the tower or mast; 
and the overall height of the transmitting antenna above ground. This 
can be combined with the sketch for the receiving location if the 
transmitting antenna is clearly shown.

[[Page 467]]

    (c) See Part 17 of this chapter concerning notification to the 
Federal Aviation Administration of proposed antenna construction or 
alteration. The provisions of Secs. 74.967 and 74.981(a)(5), concerning 
antenna painting and lighting requirements, apply to ITFS response 
stations as well as main ITFS stations.
    (d) All ITFS response stations communicating with a single 
instructional television fixed station shall operate on the same 
frequency. The specified frequency which may be used is determined by 
the channel assigned to the instructional television fixed station with 
which it is communicating, as shown in the following table. Operation on 
other ITFS response channels is prohibited.

                                                                        
------------------------------------------------------------------------
                                                       ResponseFrequency
                   ITFS Channel No.                          (MHz)      
------------------------------------------------------------------------
A-1..................................................       2686.0625   
A-2..................................................       2687.0625   
A-3..................................................       2688.0625   
A-4..................................................       2689.0625   
B-1..................................................       2686.1875   
B-2..................................................       2687.1875   
B-3..................................................       2688.1875   
B-4..................................................       2689.1875   
C-1..................................................       2686.3125   
C-2..................................................       2687.3125   
C-3..................................................       2688.3125   
C-4..................................................       2689.3125   
D-1..................................................       2686.4375   
D-2..................................................       2687.4375   
D-3..................................................       2688.4375   
D-4..................................................       2689.4375   
E-1..................................................       2686.5625   
E-2..................................................       2687.5625   
E-3..................................................       2688.5625   
E-4..................................................       2689.5625   
F-1..................................................       2686.6875   
F-2..................................................       2687.6875   
F-3..................................................       2688.6875   
F-4..................................................       2689.6875   
G-1..................................................       2686.8125   
G-2..................................................       2687.8125   
G-3..................................................       2688.8125   
G-4..................................................       2689.8125   
------------------------------------------------------------------------

    (e) Transmitter power output will normally be limited to no more 
than 250 milliwatts. Upon a special showing of need, transmitter power 
output of up to 2 watts may be permitted.
    (f) An ITFS response channel is 125 kHz wide and is centered at the 
assigned frequency. Either amplitude or frequency modulation can be 
employed. If amplitude modulation is used, the carrier shall not be 
modulated in excess of 100%. If frequency modulation is used, the 
deviation shall not exceed &177;25 kHz. Any emissions outside the 
channel including harmonics shall be attenuated at least 60 dB below 
peak output power. Greater attenuation may be required if interference 
is caused by out-of-channel emissions.
    (g) The unmodulated carrier frequency shall be maintained within 35 
kHz of the assigned frequency at all times. Adequate means shall be 
provided to insure compliance with this rule.
    (h) A directive transmitting antenna shall be employed, oriented 
toward the transmitter site of the associated instructional television 
fixed station. The beamwidth between half power points shall not exceed 
15 deg. and radiation in any minor lobe of the antenna radiation pattern 
shall be at least 20 dB below the power in the main lobe of radiation.
    (i) The transmitter of an ITFS response station may be operated 
unattended. The overall performance of the ITFS response station 
transmitter shall be checked as often as necessary to ensure that it is 
functioning in accordance with the requirements of the Commission's 
rules. The licensee of an ITFS response station is responsible for the 
proper operation of the transmitter at all times. The transmitter shall 
be installed and protected in such manner as to prevent tampering or 
operation by unauthorized persons.
    (j) The transmitting apparatus employed at ITFS response stations 
shall have received type acceptance in accordance with Sec. 74.952.
    (k) An ITFS response station shall be operated only when engaged in 
communication with its associated instructional television fixed station 
or for necessary equipment or system tests and adjustments. Radiation of 
an unmodulated carrier and other unnecessary transmissions are 
forbidden.

[ 34 FR 12101 , July 18, 1969, as amended at  35 FR 4705 , Mar. 18, 1970;  36 FR 11587 , June 16, 1971;  48 FR 44807 , Sept. 30, 1983;  52 FR 3806 , Feb. 
6, 1987;  53 FR 36788 , Sept. 22, 1988;  60 FR 55483 , Nov. 1, 1995]