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FCC Part 15 Radio Frequency Devices
Section 15.231

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: 47CFR15.231]
[Page 811-813]
                       TITLE 47--TELECOMMUNICATION
                     Subpart C_Intentional Radiators
Sec. 15.231  Periodic operation in the band 40.66-40.70 MHz and above 70 MHz.
    (a) The provisions of this section are restricted to periodic 
operation within the band 40.66-40.70 MHz and above 70 MHz. Except as 
shown in paragraph (e) of this section, the intentional radiator is 
restricted to the transmission of a control signal such as those used 
with alarm systems, door openers, remote switches, etc. Continuous 
transmissions, voice, video and the radio control of toys are not 
permitted. Data is permitted to be sent with a control signal. The 
following conditions shall be met to comply with the provisions for this 
periodic operation:
    (1) A manually operated transmitter shall employ a switch that will 
automatically deactivate the transmitter within not more than 5 seconds 
of being released.
    (2) A transmitter activated automatically shall cease transmission 
within 5 seconds after activation.
    (3) Periodic transmissions at regular predetermined intervals are 
not permitted. However, polling or supervision transmissions, including 
data, to determine system integrity of transmitters used in security or 
safety applications are allowed if the total duration of transmissions 
does not exceed more than two seconds per hour for each transmitter. 
There is no limit on the number of individual transmissions, provided 
the total transmission time does not exceed two seconds per hour.
    (4) Intentional radiators which are employed for radio control 
purposes during emergencies involving fire, security, and safety of 
life, when activated to signal an alarm, may operate during the pendency 
of the alarm condition
[[Page 812]]
    (5) Transmission of set-up information for security systems may 
exceed the transmission duration limits in paragraphs (a)(1) and (a)(2) 
of this section, provided such transmissions are under the control of a 
professional installer and do not exceed ten seconds after a manually 
operated switch is released or a transmitter is activated automatically. 
Such set-up information may include data.
    (b) In addition to the provisions of Sec. 15.205, the field 
strength of emissions from intentional radiators operated under this 
section shall not exceed the following:
                                   Field strength of   Field strength of
   Fundamental frequency (MHz)        fundamental     spurious emissions
                                  (microvolts/meter)  (microvolts/meter)
40.66-40.70.....................  2,250.............  225
70-130..........................  1,250.............  125
130-174.........................  \1\ 1,250 to 3,750  \1\ 125 to 375
174-260.........................  3,750.............  375
260-470.........................  \1\ 3,750 to        \1\ 375 to 1,250
Above 470.......................  12,500............  1,250
\1\ Linear interpolations.
    (1) The above field strength limits are specified at a distance of 3 
meters. The tighter limits apply at the band edges.
    (2) Intentional radiators operating under the provisions of this 
section shall demonstrate compliance with the limits on the field 
strength of emissions, as shown in the above table, based on the average 
value of the measured emissions. As an alternative, compliance with the 
limits in the above table may be based on the use of measurement 
instrumentation with a CISPR quasi-peak detector. The specific method of 
measurement employed shall be specified in the application for equipment 
authorization. If average emission measurements are employed, the 
provisions in Sec. 15.35 for averaging pulsed emissions and for 
limiting peak emissions apply. Further, compliance with the provisions 
of Sec. 15.205 shall be demonstrated using the measurement 
instrumentation specified in that section.
    (3) The limits on the field strength of the spurious emissions in 
the above table are based on the fundamental frequency of the 
intentional radiator. Spurious emissions shall be attenuated to the 
average (or, alternatively, CISPR quasi-peak) limits shown in this table 
or to the general limits shown in Sec. 15.209, whichever limit permits 
a higher field strength.
    (c) The bandwidth of the emission shall be no wider than 0.25% of 
the center frequency for devices operating above 70 MHz and below 900 
MHz. For devices operating above 900 MHz, the emission shall be no wider 
than 0.5% of the center frequency. Bandwidth is determined at the points 
20 dB down from the modulated carrier.
    (d) For devices operating within the frequency band 40.66-40.70 MHz, 
the bandwidth of the emission shall be confined within the band edges 
and the frequency tolerance of the carrier shall be 0.01%. This frequency tolerance shall be maintained for 
a temperature variation of -20 degrees to +50 degrees C at normal supply 
voltage, and for a variation in the primary supply voltage from 85% to 
115% of the rated supply voltage at a temperature of 20 degrees C. For 
battery operated equipment, the equipment tests shall be performed using 
a new battery.
    (e) Intentional radiators may operate at a periodic rate exceeding 
that specified in paragraph (a) of this section and may be employed for 
any type of operation, including operation prohibited in paragraph (a) 
of this section, provided the intentional radiator complies with the 
provisions of paragraphs (b) through (d) of this section, except the 
field strength table in paragraph (b) of this section is replaced by the 
                                   Field strength of   Field strength of
   Fundamental frequency (MHz)        fundamental      spurious emission
                                  (microvolts/meter)  (microvolts/meter)
40.66-40.70.....................  1,000.............  100
70-130..........................  500...............  50
130-174.........................  500 to 1,500 \1\..  50 to 150 \1\
174-260.........................  1,500.............  150
260-470.........................  1,500 to 5,000 \1\  150 to 500 \1\
Above 470.......................  5,000.............  500
\1\ Linear interpolations.
In addition, devices operated under the provisions of this paragraph 
shall be provided with a means for automatically limiting operation so 
that the duration of each transmission shall not be greater than one 
second and the silent period between transmissions shall be at least 30 
times the duration of the
[[Page 813]]
transmission but in no case less than 10 seconds.
[54 FR 17714, Apr. 25, 1989; 54 FR 32340, Aug. 7, 1989, as amended at 68 
FR 68546, Dec. 9, 2003; 69 FR 71383, Dec. 9, 2004]

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