Page:Popular Science Monthly Volume 91.djvu/810

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��Popular Science Monthly

��When stations calling each other are close by, or within easy communication distance, it is not necessary to repeat the call letters three times either in calling or acknowledging. For instance, a so-called "short call" might be as follows:

"Dash-dot-dash-dot-dash KURde KSW" and the acknowledgment or reply simply

��dot). This "End of message" signal is written as a cross (+), and, as indicated before, is often used at the end of any transmission whether of a complete mes- sage or not. The double-dash ( = ) signal, dash-dot-dot-dot-dash, is used to separate the preamble from the address, the address from the text and the text from the

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3 AM

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��FI6. 14

How the "break" or double-dash is used to separate the preamble from the address. Note the extra space between the figures for the hour and those for the minutes in the space for time filing

��the letter "K," meaning "go ahead." Such shortening of the time used for calling and establishment of communication is very helpful in working radio where much traffic is to be handled, since every minute saved for actual messages increases the number of useful words which can be put through in a given time. The formal symbols should never be abbreviated to the point where uncertainty creeps in, however, for in such cases more time is lost in repeating than would have been taken for a complete transmission in the first place.

The Authorized Message Form

Assuming that the call and reply have been given, the acknowledging station indi- cating by "K" that it is ready to receive, the calling station may begin its transmis- sion of messages. According to the Naval system (which is similar to that in use else-

��signature and should never be omitted. The preamble referred to needs further explanation. It contains the necessary information for the operators' records, and usually consists of seven parts, as follows: (i) prefix, (2) station of origin of the message, (3) number of the message, (4) the signature-letters of the sending or receiving operator, (5) the "check," or number of words in the message, (6) the date and hour the message was filed for transmission, and (7) the route or "Via," giving the call-letters or the stations which have relayed the message up to that point. The prefix is a code-letter symbol, such as "TR" for a position report giving the loca- tion of a ship at sea, "OFM"'for an official message, "SVC" for a so-called "service message" (which is one sent between sta- tions and having to do with handling mes- sages, accounts, traffic regulations, etc.),

��I I I □ I I H PTT


��□ I I I I I I I I 1 I I I I I 1 I II I I I I I I I I I I I I I I I I I I I I I 1 I I I I I I I I I I I I I I I I I I i I I I i:

��FIG. 15

The close of the specimen message, showing the double dash separating the text from the signa- ture, and the cross, or " end of the message " character, spelled out in the usual way

��where) the message transmission may be divided into six main parts, as follows: (1) Attention signal, (2) Preamble, (3) Address and route, (4) Text, (5) Signature, and (6) End of message (dot-dash-dot-dash-

��"MSG" for a private or unofficial message, or "RADIO" for a commercial message.

The name of the station (2) is spelled out, as is the day of the month under (8) — the name of the month is omitted. The num-

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