C132 



SAFETY OF LIFE AT SEA 



if the main transmitter complies with all the requirements for the reserve 

 transmitter, the latter is not obligatory. 



(c) (i) The main and reserve transmitters shall be capable of being quicklj 

 connected with and tuned to the main aerial, and the reserve aerial if or 

 is fitted. 



(ii) The main and reserve receivers shall be capable of being quicklj 

 connected with any aerial with which they are required to be used. 



(d) All parts of the reserve installation shall be placed as high in the shij 

 as is practicable, so that the greatest possible degree of safety may be secured^ 



(e) The main and reserve transmitters shall be capable of transmitting or 

 the radiotelegraph distress frequency using a class of emission assigned by the 

 Radio Regulations for that frequency. In addition, the main transmitter shall 

 be capable of transmitting on at least two of the frequencies, and of using 

 class of emission, which, in accordance with the Radio Regulations, may be 

 used for the transmission of safety messages in the bands between 405 kc/s 

 and 535 kc/s. The reserve transmitter may consist of a ship's emergencj 

 transmitter, as defined in, and limited in use by, the Radio Regulations. 



if) The main and reserve transmitters shall, if modulated emission 

 prescribed by the Radio Regulations, have a depth of modulation of not less 

 than 70 per cent, and a note frequency between 450 and 1,350 cycles pet 

 second. 



{§) The main and reserve transmitters shall, when connected to the mair 

 aerial, have a minimum normal range as specified below, that is to say, theyj 

 must be capable of transmitting clearly perceptible signals from ship to ship! 

 by day and under normal conditions and circumstances over the specified! 

 ranges* (Clearly perceptible signals will normally be received if the R.M.S. 

 value of the field strength at the receiver is at least 50 microvolts per metre.)! 



* In the absence of a direct measurement of the field strength the following data may 

 used as a guide for approximately determining the normal range; 



Normal range in miles 



Metre-amperes t 



Total aerial power (watts)J 



t This figure represents the product of the maximum height of the aerial above the deepest 

 load water line in metres and the aerial current in amperes (R.M.S. value). 



(Footnote continued on page 298) 



Ch. 4 



