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

   (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
                                   12,500.
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 following:


------------------------------------------------------------------------
                                   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 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]