ETSI ETS 300 441, Инструкция по эксплуатации

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Page 22
ETS 300 441: February 1996
8 Muting device
8.1 General
The equipment may be provided with a muting device to silence the loudspeaker until one of the following
signals is received:
a) the radiotelephone alarm signal (subclause 8.2.2);
b) the signal preceding a vital navigation warning (subclause 8.2.3);
c) additionally, the muting device may also respond to EPIRB signals as defined in the Radio
Regulations [1] provided that the signal consists of marks and spaces having a nominal duration of
one second (see subclause 8.2.4).
On reception of either of the signals a) and b) and, where appropriate, signal c), the mute shall
automatically be lifted and the equipment switched to the full audio pass band condition until manually
reset.
If this device is provided it shall be possible to set the equipment to the mute condition and restore it to
normal operation quickly and easily by means of a control available to the operator. A manual control shall
also be provided for resetting the equipment to the mute condition after the mute has been lifted.
8.2 Mute response
8.2.1 Methods of measurement
With the muting device inoperative, an A2A test signal at the carrier frequency 2 182 kHz modulated to a
depth of 30 % at 1 kHz, shall be applied to the receiver input at the measured sensitivity level. The volume
control shall be set to obtain standard output power, after which the tests as described below shall be
carried out with the mute set to the operative condition.
8.2.2 Response to the radiotelephone alarm signal
An A2A test signal modulated with the radiotelephone alarm signal to a modulation depth of 70 %, shall be
applied to the receiver input. The level shall be below that necessary to lift the mute. The output power
shall be measured whilst the level of the input test signal is increased until the output power rises to at
least - 6 dB relative to the standard output power. The input level at which this occurs shall be recorded.
The test shall be repeated at all combinations of the permitted extremes of tolerances, as given below, to
which the radiotelephone alarm signal may be subjected:
- frequency: 1 300 Hz
±
20 Hz, 2 200 Hz
±
35 Hz;
- duration of tones: 250 ms
±
50 ms;
- spacing between tones: 0 to 50 ms.
8.2.3 Response to the navigational warning signal
An A2A test signal at the carrier frequency 2 182 kHz modulated with a navigational warning signal to a
depth of 70 %, shall be applied to the receiver input. The level shall be below that necessary to lift the
mute. The output power shall be measured whilst the level of the input test signal is increased, until the
output power rises to at least - 6 dB relative to standard output power. The input level at which this occurs
shall be recorded.
The test shall be repeated at all combinations of the limits given below:
- modulation frequency: 2 200 Hz
±
35 Hz;
- modulation on: 250 ms
±
50 ms;