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FCC Part 15 Radio Frequency Devices
Section 15.115

The Federal Communications Commission (FCC) is the authority in the United States of America that creates and enforces the use of airwaves throughout the entire radio frequency spectrum. This group of documents contains the entirety of the FCC Part 15 regulations that concern unlicensed radio frequency devices. As with all government documents, this material is in the public domain and may be freely copied so long as the content is not changed. This copy is provided as a convenience for RF Cafe visitors. 

Click here for the Table of Contents.
[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2008]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.115]
[Page 771-773]
 
                       TITLE 47--TELECOMMUNICATION
 
              CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION
 
PART 15_RADIO FREQUENCY DEVICES--Table of Contents
 
                    Subpart B_Unintentional Radiators
 
Sec. 15.115  TV interface devices, including cable system terminal devices.
    (a) Measurements of the radiated emissions of a TV interface device 
shall be conducted with the output terminal(s) of the device terminated 
by a resistance equal to the rated output impedance. The emanations of a 
TV interface device incorporating an intentional radiator shall not 
exceed the limits in Sec. 15.109 or subpart C of this part, whichever 
is higher for each frequency. Where it is possible to determine which 
portion of the device is contributing a particular radio frequency 
emission, the emissions from the TV interface device portion shall 
comply with the emission limits in Sec. 15.109, and the emissions from 
the intentional radiator shall comply with subpart C of this part.
    (b) Output signal limits:
    (1) At any RF output terminal, the maximum measured RMS voltage, in 
microvolts, corresponding to the peak envelope power of the modulated 
signal during maximum amplitude peaks across a resistance (R in ohms) 
matching the rated output impedance of the TV interface device, shall 
not exceed the following:
    (i) For a cable system terminal device or a TV interface device used 
with a master antenna, 692.8 times the square root of (R) for the video 
signal and 155 times the square root of (R) for the audio signal.
 
[[Page 772]]
    (ii) For all other TV interface devices, 346.4 times the square root 
of (R) for the video signal and 77.5 times the square root of (R) for 
the audio signal.
    (2) At any RF output terminal, the maximum measured RMS voltage, in 
microvolts, corresponding to the peak envelope power of the modulated 
signal during maximum amplitude peaks across a resistance (R in ohms) 
matching the rated output impedance of the TV interface device, of any 
emission appearing on frequencies removed by more than 4.6 MHz below or 
7.4 MHz above the video carrier frequency on which the TV interface 
device is operated shall not exceed the following:
    (i) For a cable system terminal device or a TV interface device used 
with a master antenna, 692.8 times the square root of (R).
    (ii) For all other TV interface devices, 10.95 times the square root 
of (R).
    (3) The term master antenna used in this section refers to TV 
interface devices employed for central distribution of television or 
other video signals within a building. Such TV interface devices must be 
designed to:
    (i) Distribute multiple television signals at the same time;
    (ii) Distribute such signals by cable to outlets or TV receivers in 
multiple rooms in the building in which the TV interface devices are 
installed; and,
    (iii) Distribute all over-the-air or cable signals.
    Note: Cable-ready video cassette recorders continue to be subject to 
the provisions for general TV interface devices.
    (c) A TV interface device shall be equipped with a transfer switch 
for connecting the antenna terminals of a receiver selectively either to 
the receiving antenna or to the radio frequency output of the TV 
interface device, subject to the following:
    (1) When measured in any of its set positions, transfer switches 
shall comply with the following requirements:
    (i) For a cable system terminal device or a TV interface device 
equipped for use with a cable system or a master antenna, as defined in 
paragraph (b)(3) of this section, the isolation between the antenna and 
cable input terminals shall be at least 80 dB from 54 MHz to 216 MHz, at 
least 60 dB from 216 MHz to 550 MHz and at least 55 dB from 550 MHz to 
806 MHz. The 80 dB standard applies at 216 MHz and the 60 dB standard 
applies at 550 MHz. In the case of a transfer switch requiring a power 
source, the required isolation shall be maintained in the event the 
device is not connected to a power source or power is interrupted. The 
provisions of this paragraph regarding frequencies in the range 550 MHz 
to 806 MHz are applicable as of June 30, 1997.
    (ii) For all other TV interface devices, the maximum voltage, 
corresponding to the peak envelope power of the modulated video signal 
during maximum amplitude peaks, in microvolts, appearing at the 
receiving antenna input terminals when terminated with a resistance (R 
in ohms) matching the rated impedance of the antenna input of the 
switch, shall not exceed 0.346 times the square root of (R).
    (iii) Measurement to determine compliance with the transfer switch 
limits shall be made using a connecting cable, where required, between 
the TV interface device and the transfer switch of the type and length:
    (A) Provided with the TV interface device,
    (B) Recommended in the instruction manual, or
    (C) Normally employed by the consumer.
    (2) A TV interface device shall be designed and constructed, to the 
extent practicable, so as to preclude the possibility that the consumer 
may inadvertently attach the output of the device to the receiving 
antenna, if any, without first going through the transfer switch.
    (3) A transfer switch is not required for a TV interface device 
that, when connected, results in the user no longer having any need to 
receive standard over-the-air broadcast signals via a separate antenna. 
A transfer switch is not required to be marketed with a cable system 
terminal device unless that device provides for the connection of an 
external antenna. A transfer switch is not required for a device that is 
intended to be used as an accessory to an authorized TV interface 
device.
    (4) An actual transfer switch is not required for a TV interface 
device, including a cable system terminal device,
[[Page 773]]
that has an antenna input terminal(s); provided, the circuitry following 
the antenna input terminal(s) has sufficient bandwidth to allow the 
reception of all TV broadcast channels authorized under part 73 of this 
chapter and: For a cable system terminal device that can alternate 
between the reception of cable television service and an antenna, 
compliance with the isolation requirement specified in paragraph 
(c)(1)(i) of this section can be demonstrated; and, for all other TV 
interface devices, the maximum voltage appearing at the antenna 
terminal(s) does not exceed the limit in paragraph (c)(1)(ii) of this 
section.
    (5) If a transfer switch is not required, the following label shall 
be used in addition to the label shown in Sec. 15.19(a):
    This device is intended to be attached to a receiver that is not 
used to receive over-the-air broadcast signals. Connection of this 
device in any other fashion may cause harmful interference to radio 
communications and is in violation of the FCC Rules, part 15.
    (d) A TV interface device, including a cable system terminal device, 
shall incorporate circuitry to automatically prevent emanations from the 
device from exceeding the technical specifications in this part. These 
circuits shall be adequate to accomplish their functions when the TV 
interface device is presented, if applicable, with video input signal 
levels in the range of one to five volts; this requirement is not 
applicable to a TV interface device that uses a built-in signal source 
and has no provisions for the connection of an external signal source. 
For devices that contain provisions for an external signal source but do 
not contain provisions for the input of an external baseband signal, 
e.g., some cable system terminal devices, compliance with the provisions 
of this paragraph shall be demonstrated with a radio frequency input 
signal of 0 to 25 dBmV.
    (e) For cable system terminal devices and TV interface devices used 
with a master antenna, as defined in paragraph (b)(3) of this section, 
the holder of the grant of authorization shall specify in the 
instruction manual or pamphlet, if a manual is not provided, the types 
of wires or coaxial cables necessary to ensure that the unit complies 
with the requirements of this part. The holder of the grant of 
authorization must comply with the provisions of Sec. 15.27. For all 
other TV interface devices, the wires or coaxial cables used to couple 
the output signals to the TV receiver shall be provided by the 
responsible party.
    (f) A TV interface device which is submitted to the Commission as a 
composite device in a single enclosure containing a RF modulator, video 
source and other component devices shall be submitted on a single 
application (FCC Form 731) and shall be authorized as a single device.
    (g) An external device or accessory that is intended to be attached 
to a TV interface device shall comply with the technical and 
administrative requirements set out in the rules under which it 
operates. For example, a personal computer must be certificated to show 
compliance with the regulations for digital devices.
    (h) Stand-alone switches used to alternate between cable service and 
an antenna shall provide isolation between the antenna and cable input 
terminals that is at least 80 dB from 54 MHz to 216 MHz, at least 60 dB 
from 216 MHz to 550 MHz and at least 55 dB from 550 MHz to 806 MHz. The 
80 dB standard applies at 216 MHz and the 60 dB standard applies at 550 
MHz. In the case of stand-alone switches requiring a power source, the 
required isolation shall be maintained in the event the device is not 
connected to a power source or power is interrupted. The provisions of 
this paragraph are applicable as of June 30, 1997.
    (i) Switches and other devices intended to be used to by-pass the 
processing circuitry of a cable system terminal device, whether internal 
to such a terminal device or a stand-alone unit, shall not attenuate the 
input signal more than 6 dB from 54 MHz to 550 MHz, or more than 8 dB 
from 550 MHz to 804 MHz. The 6 dB standard applies at 550 MHz. The 
provisions of this paragraph are applicable June 30, 1997.
[54 FR 17714, Apr. 25, 1989, as amended at 57 FR 33448, July 29, 1992; 
59 FR 25341, May 16, 1994; 61 FR 18509, Apr. 26, 1996]
[[Page 774]]



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