C136 SAFETY OF LIFE AT SEA 



Regulation 10 



Radiotelegraph Auto Alarms 



(a) Any radiotelegraph auto alarm installed after the date of coming into 

 force of the present Convention shall comply with the following minimum 

 requirements : — 



(i) In the absence of interference of any kind it shall be capable of 

 being actuated, without manual adjustment, by any radio- 

 telegraph alarm signal transmitted on the radiotelegraph distress 

 frequency by any coast station, ship'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. 



(ii) 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. 



(iii) 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 indicated in (ii). 



(iv) 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 kc/s and not more than 8 kc/s 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. 



(v) If practicable, the radiotelegraph auto alarm 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. 



(vi) When actuated by a radiotelegraph alarm signal, or in the event of 

 failure of the apparatus, the radiotelegraph auto alarm shall cause 

 a continuous audible warning to be given in the radiotelegraph 

 operating room, in the radio officer's sleeping accommodation and 

 on the bridge. 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. 



(vii) For the purpose of regularly testing the radiotelegraph auto alarm, 

 the apparatus shall include a generator pre-tuned to the radio- 

 telegraph distress frequency and a keying device by means of 



Ch. 4 



