Sec.  80.269   Technical requirements for radiotelephone distress frequency watch
receiver.

   (a) The radiotelephone distress frequency watch receiver is comprised of a
   receiver, a loudspeaker and a radiotelephone auto alarm device.

   (b) The radiotelephone distress frequency watch receiver must meet the
   following requirements:

   (1) The receiver must be capable of being switched to 2182 kHz and of
   receiving signals of at least A2A and A2B emissions;

   (2) The receiver sensitivity must provide a SINAD of 20 dB at the audio
   output when a 30 microvolt signal with A2A or A2B emission modulated 30% at
   400 Hz is applied to the receiver RF terminals;

   (3) The audio output of the receiver must be at least 50 milliwatts at the
   rated load impedance;

   (4) The receiver must be provided with an auto alarm device which mutes the
   receiver (silences the loudspeaker) unless the radiotelephone alarm signal
   or the signal preceeding a vital navigational warning is received. When the
   auto alarm is activated the receiver audio output level must be louder than
   the output level of the received speech signal. Additionally, the receiver
   must meet the following requirements:

   (i) When the receiver is muted its audio output power must be less than 1
   milliwatt;

   (ii) If tone filters are used to process the 1300 Hz and 2200 Hz tones the
   tolerance of their center frequency must be  ±1.5 percent of the alerting
   frequency. The response must be flat within 6 dB to  ±3% of the center
   frequency of the filters; and

   (iii) The receiver must not be unmuted by atmospherics or by strong signals
   other than the radiotelephone alarm and the vital navigational warning
   signal.

   (5) The receiver must be unmuted within 4 to 6 seconds when a double
   sideband alarm signal modulated at 70% is applied at its input terminals at
   a level which produces a SINAD of 10 dB under the following conditions:

   (i) For radiotelephone alarm the signal must be modulated sequentially by a
   1300  ±20 Hz tone and a 2200  ±35 Hz tone. The duration of each tone must be
   250  ±50 milliseconds and the period between each tone must not exceed 50
   milliseconds; and

   (ii) For navigational warning the signal must be modulated by a 2200  ±35 Hz
   tone and the modulated carrier must be turned “on” for 250  ±50 milliseconds
   and then “off” for 250  ±50 milliseconds.

   (6) The receiver must not be unmuted when a double sideband signal of 70 dB
   above the receiver measured sensitivity, modulated at 70% by a 2200  ±35 Hz
   tone with the following durations is applied at its input terminals:

   (i) “On” periods of less than 175 milliseconds or more than 325 milliseconds
   followed by “off” periods of any duration; and

   (ii) “Off” periods of less than 175 milliseconds or more then 425
   milliseconds followed by “on” periods of any duration.

   (7) The controls listed below must be provided on the exterior of the
   equipment:

   (i) On/off switch with a visual indication that the device is on;

   (ii) Volume control to adjust the audio output;

   (iii) Control for dimming any light on the equipment;

   (iv) Control for switching the auto alarm in and out of operation; and

   (v) Control to manually reset the auto alarm to muted condition.

   (8) The receiver must operate within specifications throughout the
   temperature range 0–50 degrees Celsius at relative humidities as high as
   95%.

   (9) The receiver must be capable of operating when subjected to vibrations
   having a frequency between 20 and 30 Hertz and an amplitude of 0.76 mm (0.03
   inch) in a direction at an angle of 30 to 45 degrees with the base of the
   auto alarm.

   [ 51 FR 31213 , Sept. 2, 1986, as amended at  58 FR 44952 , Aug. 25, 1993;  68 FR 46966 , Aug. 7, 2003]