Goto Section: 15.229 | 15.233 | Table of Contents
Revised as of September 1, 2021
Goto Year:2020 |
§ 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
(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 § 15.205, the field strength of
emissions from intentional radiators operated under this section shall
not exceed the following:
Fundamental frequency (MHz) Field strength of fundamental
(microvolts/meter) Field strength of spurious emissions
40.66-40.70 2,250 225
70-130 1,250 125
130-174 ^11,250 to 3,750 ^1125 to 375
174-260 3,750 375
260-470 ^13,750 to 12,500 ^1375 to 1,250
Above 470 12,500 1,250
(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 § 15.35 for averaging
pulsed emissions and for limiting peak emissions apply. Further,
compliance with the provisions of § 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 § 15.209, whichever limit permits a higher field
(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 Â±0.01%. This
frequency tolerance shall be maintained for a temperature variation of
âˆ’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
Fundamental frequency (MHz) Field strength of fundamental
(microvolts/meter) Field strength of spurious emission
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
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 transmission but in no case less than 10
[ 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]
Goto Section: 15.229 | 15.233
Goto Year: 2020 |
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