SIGNALLING WITH THE HELIOGRAPH 179 



be sent with this code quite as rapidly as with the Myer code and only a little 

 less rapidly than with the International Morse code. The fact that each letter con- 

 sists of only two symbols, and that only dots are sent and no dashes, makes it an easier 

 code to send intelligibly and to read. The further fact that it is made according to 

 a simple rule as already explained, is an advantage in forest-protection work, where 

 the use of the heliograph is confined to a limited portion of the year and where 

 operators will generally not be able to keep in practice. In the district where this 

 code is employed for forest-protection communication the following numerals and 

 conventional signals have been adopted: 



NUMERALS 



B 1 G 



C 2 H 



D '. . 3 I 



E 4 J 



F . . 5 M 



CONVENTIONAL SIGNALS 



End of word Interval (2 seconds) 



End of sentence or message. . 1-6 Wait a moment 6-1 



I understand 2-6 Signal faster 6-2 



Repeat last word 3-6 Cease signalling 6-3 



Repeat last message 4-6 I wish to use message code . . 6-4 



Section 113 Instructions to Operators 



In sending with the heliograph it is of the utmost importance that uniformity 

 in mechanical movements of the screen be cultivated, as lack of rhythm in the signals 

 of the sender entails unnecessary and vexatious concentration of attention on the 

 part of the receiver. 



The first position is to turn a steady flash on the receiving station. The signals 

 are made by long and short flashes. Use <a short flash for dot and a long steady flash 

 for a dash. The elements of a letter should te slightly longer than in sound signals. 



To call a station. Send a rapid succession of short flashes until acknowledged. 

 Each station will then turn 011 a steady flash and adjust. When the adjustment is 

 satisfactory to the called station it will cut off its flash .and? the calling station will 

 proceed with its message. 



Adjustment. If the receiver sees that the sender's mirror needs adjustment, he 

 will turn on a steady flash until answered by a steady flash. When the adjustment 

 is satisfactory the receiver will cut off his flash iand the sender will resume his 

 message. 



To break or stop the signals from the sending station. -Make a rapid succession 

 of short flashes without pause until the sender stops sending. 



To start the sending station after IreaHng. Turn on a long flash and he will 

 commence at the 'beginning of last word. 



To acknowledge receipt of a message. Signal - - followed by the name 



of the receiver. 



If the sender discovers that he hus made an error he should make a rapid succes- 

 sion of short flashes, after which he begins with the word in which the error occurred. 



To lessen liability of error, numerals which occur in the body of a message 

 .should be spelled out in full. 



7921112* 



