In the preparation of codes for signals with rockets or bombs there should always be arranged a "preparatory signal" which means "Are you ready?" etc., and an "answering signal," which means "Repeat your last signal," etc., a signal "annul," which means "Disregard last signal," and a signal to signify the correct receipt of the complete message, or "Signal seen and understood." [Illustration: TWO-ARM SEMAPHORE ALPHABET, U. S. NAVY.] [Illustration] [Illustration] CONVENTIONAL SIGNALS. End of word see instructions. End of message see instructions. Error see instructions. Repeat last word =C=, 'end of word', once. Repeat last message =C=, 'end of word', 3 times. Use paper and pencil =P=, 'end of word', twice. ABBREVIATIONS. =A= "end of word" after =B= " " " before =C= " " " can =H= " " " have =N= " " " not =R= " " " are =T= " " " the =U= " " " you =UR= " " " your =W= " " " word =WI= " " " with =Y= " " " yes =PG= " " " permission granted =NG= " " " permission not granted =XX= " " " numerals follow [Illustration: SUMMARY OF SIGNALS, ARMY AND NAVY ALPHABET.] CHAPTER IV. THE FIELD MESSAGE. _Definition._--The term "field message" is applied to all messages sent over field lines of information. All field messages for transmission over field lines of information by electrical or visual means should be plainly written by the sender on the blank forms in the United States Army Field Message Book. The practice of verbally delivering telegrams to enlisted men for transmission should invariably be discouraged. "In framing telegrams, all words not important to the sense will be omitted. The last name of the officer addressed, or his title, and the last name of the sender are generally sufficient." (Paragraph 1198, Army Regulations.) _The blank form._--The United States Army Field Message Book issued by the Signal Corps is 4-5/8 inches wide by 6¾ inches long, and contains 40 message blanks with duplicate tissue sheets and two sheets of carbon paper. The message is written on the yellow sheet, which can be torn out for delivery. The carbon sheet is attached to the book, and contrary to the custom in most carbon duplicating books, is placed _under_ the tissue sheet when a message is being written. When not being used, the carbon sheet should invariably be kept in the back of the book. When the upper carbon sheet has become worn out, it should be torn out and the second carbon sheet used instead. The blank form is shown in figure 16. The back of the blank is ruled in squares and provided with scales for use in making sketches. [Illustration: