Artikel 138

(1) A radiotelegraph auto alarm shall comply with the following minimum requirements: (a) in the absence of interference of any kind it shall be capable of being actuated, without manual adjustment, by any radiotelegraph alarm signal transmitted on the radiotelegraph distress frequency by any coast station, ship's or vessel's emergency or survival craft transmitter operating in accordance with the Radio Regulations, provided that the strength of the signal at the receiver input is greater than 100 microvolts and less than 1 volt;
(b) in the absence of interference of any kind it shall be actuated by either three or four consecutive dashes when the dashes vary in length from 3.5 to as near 6 seconds as possible and the spaces vary in length between 1.5 seconds and the lowest practicable value, preferably not greater than 10 milliseconds;
(c) it shall not be actuated by atmospherics or by any signal other than the radiotelegraph alarm signal, provided that the received signals do not in fact constitute a signal falling within the tolerance limits referred to in sub-paragraph (b);
(d) the selectivity of the radiotelegraph auto alarm shall be such as to provide a practically uniform sensitivity over a band extending not less than 4 kilohertz and not more than 8 kilohertz on each side of the radiotelegraph distress frequency and to provide outside this band a sensitivity which decreases as rapidly as possible in conformity with the best engineering practice;
(e) if practicable, it shall, in the presence of atmospherics or interfering signals, automatically adjust itself so that within a reasonably short time it approaches the condition in which it can most readily distinguish the radiotelegraph alarm signal;
(f) when actuated by a radiotelegraph alarm signal, or in the event of failure of the apparatus, it shall cause a continuous audible warning to be given in the radiotelegraph operating room, in the radio officer's or radio operator's sleeping accommodation and in the wheelhouse. If practicable, warning shall also be given in the case of failure of any part of the whole alarm receiving system. Only one switch for stopping the warning shall be provided and this shall be situated in the radiotelegraph operating room;
(g) for the purpose of regularly testing the radiotelegraph auto alarm, the apparatus shall include a generator pre-tuned to the radiotelegraph distress frequency and a keying device by means of which a radiotelegraph alarm signal of the minimum strength referred to in sub-paragraph (a) is produced. Means shall also be provided for attaching headphones for the purpose of listening to signals received on the radiotelegraph auto alarm; and
(h) all be capable of withstanding vibration, humidity and anges of temperature, equivalent to severe conditions experienced on board vessels at sea, and shall continue to operate under such conditions.
(a) in the absence of interference of any kind it shall be capable of being actuated, without manual adjustment, by any radiotelegraph alarm signal transmitted on the radiotelegraph distress frequency by any coast station, ship's or vessel's emergency or survival craft transmitter operating in accordance with the Radio Regulations, provided that the strength of the signal at the receiver input is greater than 100 microvolts and less than 1 volt;
(b) in the absence of interference of any kind it shall be actuated by either three or four consecutive dashes when the dashes vary in length from 3.5 to as near 6 seconds as possible and the spaces vary in length between 1.5 seconds and the lowest practicable value, preferably not greater than 10 milliseconds;
(c) it shall not be actuated by atmospherics or by any signal other than the radiotelegraph alarm signal, provided that the received signals do not in fact constitute a signal falling within the tolerance limits referred to in sub-paragraph (b);
(d) the selectivity of the radiotelegraph auto alarm shall be such as to provide a practically uniform sensitivity over a band extending not less than 4 kilohertz and not more than 8 kilohertz on each side of the radiotelegraph distress frequency and to provide outside this band a sensitivity which decreases as rapidly as possible in conformity with the best engineering practice;
(e) if practicable, it shall, in the presence of atmospherics or interfering signals, automatically adjust itself so that within a reasonably short time it approaches the condition in which it can most readily distinguish the radiotelegraph alarm signal;
(f) when actuated by a radiotelegraph alarm signal, or in the event of failure of the apparatus, it shall cause a continuous audible warning to be given in the radiotelegraph operating room, in the radio officer's or radio operator's sleeping accommodation and in the wheelhouse. If practicable, warning shall also be given in the case of failure of any part of the whole alarm receiving system. Only one switch for stopping the warning shall be provided and this shall be situated in the radiotelegraph operating room;
(g) for the purpose of regularly testing the radiotelegraph auto alarm, the apparatus shall include a generator pre-tuned to the radiotelegraph distress frequency and a keying device by means of which a radiotelegraph alarm signal of the minimum strength referred to in sub-paragraph (a) is produced. Means shall also be provided for attaching headphones for the purpose of listening to signals received on the radiotelegraph auto alarm; and
(h) all be capable of withstanding vibration, humidity and anges of temperature, equivalent to severe conditions experienced on board vessels at sea, and shall continue to operate under such conditions.
(2) Before a new type of radiotelegraph auto alarm is approved, the Administration shall be satisfied, by practical tests made under operating conditions equivalent to those obtaining in practice, that the apparatus complies with paragraph (1).
(3) In vessels fitted with a radiotelegraph auto alarm, its efficiency shall be tested by a radio officer or radio operator at least once every 24 hours while at sea. If it is not in working order, the radio officer or radio operator shall report that fact to the skipper or officer on watch.
(4) A radio officer or radio operator shall periodically check the proper functioning of the radiotelegraph auto alarm receiver, with its normal antenna connected, by listening to signals and by comparing them with similar signals received on the radiotelegraph distress frequency on the main installation.
(5) As far as practicable, the radiotelegraph auto alarm, when connected to an antenna, shall not affect the accuracy of the direction-finder.