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. Radio control of 
toys is not permitted. Continuous transmissions, such as voice or video, 
and data transmissions are not permitted. The prohibition against data 
transmissions does not preclude the use of recognition codes. Those 
codes are used to identify the sensor that is activated or to identify 
the particular component as being part of the system. 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 to 
determine system integrity of transmitters used in security or safety 
applications are allowed if the periodic rate of transmission does not 
exceed one transmission of not more than one second duration per hour 
for each transmitter.
    (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
    (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:

[[Page 659]]



                                                                        
------------------------------------------------------------------------
                                   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 &177;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]