§  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

   (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
   (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 12,500 ^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 §  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 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 following:
   Fundamental frequency (MHz) Field strength of fundamental
   (microvolts/meter) Field strength of spurious emission
   (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 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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