Popular Science Monthly 



795 



ber of the message, the "check" or number 

 of words, and the hour in (8) are given in 

 figures, the hour being followed by "am" or 

 "pm." Sometimes the signature letters 

 of the sending operator are merely written 

 on the blank and not transmitted, but this 

 omission may give rise to confusion be- 

 tween the number of the message and the 

 "check." 



A Specimen Message 



Let us consider a typical message to be 

 transmitted from Philadelphia (call letters 

 NAI) to New York (call letters WHB), on 

 commercial matters, and sent by an opera- 

 tor at Philadelphia who has adopted the 

 letters XM as his personal identification 

 signature — letters or "sign." This 

 might be as follows: 



3, 1917, 



Philadelphia, Pa., Nov 

 Filed 11:03 a. m 

 To James Doherty, 



Equitable Building, New York. 

 Express twelve thousand item seven 

 drawing eight two. 



Duncan. 



As sent out by the Phila- 

 delphia operator, assuming 

 it to be the fifth message 

 sent to New York that 

 day, it would be as given 

 below. Each section is 

 given separately, so that it 

 may be compared with the 

 list of parts just stated: 



"Dash-dot-dash-dot-dash 



RADIO 



Philadelphia 



5 



X M 



14 



THIRD 



1 103 a m 



Dash-dot-dot-dot-dash 



James Doherty Equitable 

 Building Newyork 



Dash-dot-dot-dot-dash 



Express twelve thousand item seven drawing 

 eight-two 



Dash-dot-dot-dot-dash 



Duncan 



Dot-dash-dot-dash-dot 



Taking up these lines in sequence, we 

 find first the attention signal and then the 

 prefix. This is followed by the station's 

 name, spelled out, and by the number of 

 the message (namely, 5). Next come the 

 operator's sign and the check, or number 

 of words in the message. It is difficult to 

 see just how the specimen message contains 

 fourteen words until one knows that the 



Radio waves sent 

 in all directions 

 from several sta- 

 tions may overlap 

 and create consider- 

 able "interference" 



check includes the words in tne address, 

 text and signature (according to "cable 

 count") and notes that names of cities 

 such as New York and New Orleans and 

 states such as West Virginia are counted as 

 single words in addresses but as two words 

 when they appear in the text. The rest of 

 the message should be perfectly clear 

 without further explanation, though it may 

 be noted that no relays or via's, and no 

 route for addressing appear in such a simple 

 transmission as that assumed for this 

 example. 



Sending Messages in Sequence 



When the sending sta- 

 tion has several messages 

 to transmit to the same 

 receiver, the operator may 

 follow with the second and 

 third immediately after the 

 first ; it is not a good plan 

 to send too many in se- 

 quence without giving the 

 receiving station an oppor- 

 tunity to acknowledge and ask 

 for any corrections or confirma- 

 tions which may be necessary. 

 After sending one or two messages 

 the sending operator should "sign 

 off" with his station call and 

 make the "go ahead" signal 

 "K"), after which the receiv- 

 ing station will call and send 

 "R R R" if he has received 

 everything correctly or "? ? ?" 

 to indicate repetitions desired. 

 The method of indicating partial 

 repetitions necessary to fill in 

 doubtful words or phrases was 

 indicated in the September arti- 

 cle, and need not be given again 

 here. When all messages in both 

 directions have been transmitted 

 and satisfactorily received, the 

 Dot-dot-dot-dash-dot-dash, which 

 'finished," is sent out by both 



signal 

 means ' 

 stations. 



Complicated as all this may seem to the 

 beginner, it is a system of communication 

 which is quickly learned and which contains 

 little or nothing that is not essential when 

 many different stations are involved in the 

 traffic system. Naturally enough, when 

 two plants (such as Sayville and Nauen) 

 communicate with each other exclusively 

 it is possible to eliminate a large part of the 

 preamble. Messages may be sent without 

 confusion by giving nothing but the num- 



