CHAPTER XXIV 



MESSAGE CODES 



Section 128 Purpose of Codes 



Message codes are devised in order that preconcerted phrases or sentences may 

 be expeditiously transmitted. They are widely employed in various lines of activity 

 and can be made extremely useful in forest-protection communication, especially 

 where methods of communication other than the telephone are relied upon and the 

 operators have had only limited training. In these codes, one, two, or three letters 

 of the alphabet are used to designate each prearranged sentence, and' by having a 

 well arranged copy of the code at each station it is possible to send and receive whole 

 sentences or messages in the time needed to transmit only these one, two, or three 

 letters. 



Section 129 Use in Forest Protection 



A message code is particularly adaptable to forest fire detection work. The first 

 code used in forest protection was- employed by the author, with lookout stations 

 equipped with heliographs, in 1909. Others have since been devised, the latest being 

 that of the United States Forest Service in District 1, issued in May, 1916. To a 

 certain extent it is necessary to devise a code to fit the conditions of operation, and 

 the main problem lies in anticipating the messages that it will be necessary for the 

 operator to send. Thus far, mesisage codes have been employed only for the sending 

 of messages from lookout stations. A code of this sort is given in the " Dominion 

 Forestry Branch Message Code" (see note below). This code will be employed for 

 signal communication on Dominion forest reserves wherever signal equipment is 

 installed. If it is found necessa-ry to alter or extend it to fit local conditions this 

 may readily be done by following the rules for preparation given in the " Dominion 

 Forestry Branch Message Code." 



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Section 130 Combinations Available 



With two letters of the alphabet in each signal and with no repetition of a letter 

 in any display, 624 combinations are possible, and each may represent a prearranged 

 phrase, sentence, or message. By using the single letters of the alphabet and also 

 such combinations as A A, B B, etc. 52 additional signals may be obtained, making 

 676 in all. From these, however, it will be advisable to eliminate the various letters 

 and combinations usecfr as conventional signals in the International and other codes, 

 but there will still remain well over 650 available combinations. 



Six hundred and fifty phrases give a range of possibilities that covers rather 

 fully the urgent messages that need to be sent by one lookout man to another, or to 

 headquarters, and the saving in time is apparent when it is considered for instance 

 that by sending simply two code letters the lookout man may be enabled to transmit 

 such a message as : "I have sighted a fire, the azimuth bearing of which from my 

 station is 24 degrees." 



If 650 signals are not sufficient, by using combinations of three letters in addi- 

 tion to those composed of one and two, more than 16,000 different signals are made 

 available. 



]\T fp The preceding sections deal with codes in general, their purpose and 

 scope. The particular code prepared for the use of the officers of the Dominion 

 Forpstrii Branch is, for convenience, published in the form of a small, separate book 

 entitled "Dominion Forestry Branch Message Code." 



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