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, A2B, H2A and H2B emissions;
    (2) The receiver sensitivity must provide a SINAD of 20 dB at the 
audio output when a 30 microvolt signal with A2A, A2B, H2A, or H2B 
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 &177;1.5 
percent of the alerting frequency. The response must be flat within 6 dB 
to &177;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 &177;20 Hz tone and a 2200 &177;35 
Hz tone. The duration of each tone must be 250 &177;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 
&177;35 Hz tone and the modulated carrier must be turned ``on'' 
for 250 &177;50 milliseconds and then ``off'' for 250 
&177;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 &177;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]

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