Chapter IX¹
Communications[‡]

The HTML character set does not include the ability to represent overscores. We have adopted the convention of representing these as underscores instead. Hence: "AAA" should be read as , etc. --HyperWar

Section A

Policy for Coordination of Radio Activities of the Army and Navy

1. Joint Board reports, J.B. No. 319 (Serial No. 183), of January 16, 1923, "Utilization of the radio services of the War and Navy Departments for the transmission of Government despatches," and J.B. No. 319 (Serial No. 253), "Proposed draft of Executive Orders re regulation of radio in the event of war or national emergency," are rescinded. The following policy, approved by the Secretary of War and the Secretary of the Navy, is published for information and guidance:
1. Purpose of Radio Policy.

   2. The purpose of this statement of policy is to establish an authoritative bases for the coordination of the Army and Navy in the development of radio material, the establishment of radio stations, and in the conduct of radio activities.

2. Basic Policy.

   3. The Army and Navy shall provide, control, and operate such transmitting and receiving stations as, augmented by private and

other Government-owned radio facilities, will insure the existence and availability upon the outbreak of war or other national emergency of a militarily controlled, thoroughly indoctrinated radio system adequate to meet the requirements of national defense, having in view the prevention of undesirable duplication and the practical and definite limitation on expenditure imposed by economy.
3. Primary Responsibility of the Army and Navy in Radio Activities.

   4. 1. The assignment of primary responsibility to the Army or to the Navy for radio activities serving a definite area or purpose imposes upon the designated service the responsibility for the establishment and efficiency of radio serving such area or purpose, but allows the other service to use radio to serve the same area or its own purposes of a similar nature, provided no serious radio interference is caused thereby.

      2. In war time paramount interest in certain areas or theaters of operation will be assigned to the Army or the Navy, in accordance with the approved War Plans, and radio activities therein will be coordinated by the responsible commander of the service having paramount interest.

      3. In order to avoid uneconomical duplication in time of peace:

         1. The Navy only shall operate radio apparatus of high power (10 kilowatts in the antenna or greater).

         2. The Army shall not handle overseas radio communications commercially or for other Government departments except between the United States and Alaska, nor operate upon frequencies which will cause serious interference with Fleet or Navy overseas circuits.

4. Assignment of Primary Responsibility.

   5. Subject to the provisions of subparagraphs (a) and (b) of the preceding paragraph, primary responsibility is assigned as follows:

      1. To the Army in radio communication--

         1. With and between Army units wherever located.

         2. Within the Territory of Alaska.

         3. With and between Army vessels, excluding such vessels as may be placed under Navy control.

      2. To the Army in radio intelligence--

         1. For the Army wherever operating.

3. To the Navy in radio communication--

   1. For the establishment, maintenance, and operation of an overseas radio service for efficient communication with and between Navy units wherever located; this service to be available to all departments of the Government and for commercial purposes.

   2. For communication with insular possessions, the Panama Canal Zone, and with foreign territory occupied by the Navy.

   3. With and between ships at sea, exclusive of Army vessels, except such of the latter as may have been placed under Navy control in case of war or national emergency.

   4. For the establishment and operation of radio-compass stations along the coasts of the United States, Alaska, overseas possessions, or occupied foreign territory.

4. To the Navy in radio intelligence--

   1. For the Navy wherever operating.
5. War-time Jurisdiction over Nonmilitary Radio.

   6. In time of national emergency, when directed by the President according to law, the Army and the Navy will assume jurisdiction as follows:

      1. The Army and Navy shall each assume complete control over such nonmilitary radio stations as may be allocated to them by the President to augment their peace-time facilities.

      2. For purposes of censorship and supervision over such nonmilitary radio stations as are permitted to operate:

         1. The Army will assume jurisdiction over all nonmilitary stations within the United States, Alaska, and foreign territory occupied by the Army except the stations assigned to the Navy in the following paragraph:

         2. The Navy will assume jurisdiction over all nonmilitary stations wherever located that are permitted to communicate overseas, with ships, or with aircraft flying over the sea other than Army aircraft, and over all nonmilitary stations in Panama, the insular possessions, and in foreign territory exclusively occupied by the Navy.

3. For the purpose of suppression of unauthorized radio:

   1. The Army will assume jurisdiction over the continental United States, Alaska, Panama, and in insular possessions or foreign territory occupied by the Army.

   2. The Navy will assume jurisdiction over shipping and over insular possessions or foreign territory occupied exclusively by the Navy.
6. Principles to be Observed in Radio Coordination.

   7. Coordination in radio operation will be effected:

      1. In the development of types of radio equipment suitable for intercommunications.

      2. By the assignment of call letters, frequencies, transmitting time periods, the adoption of a common procedure, and the formulation of codes and ciphers for joint Army and Navy communication.

      3. All air radio stations of the Navy and air radio stations of the Army along the coast and in the insular and outlying possessions shall be equipped to send and receive on a common intermediate frequency and a common high frequency, and all aircraft carrying radio, except fighting and pursuit planes, shall as soon as practicable, consistent with proper economy, be equipped to send and receive on one of these common frequencies.

      4. The radio field sets provided for the use of the Marine Crops on shore shall be capable of intercommunication with the radio provided for the operation of similarly equipped units of the Army.

      5. The radio communication equipment provided for the vessels of the Army Transport Service shall be of a character normally provided for commercial shipping of the same general class and shall be capable of sending and receiving on at least two frequencies assigned by the Navy Department for Naval Transportation Service communication.

7. Coordination with Radio Stations of Other Departments and Civilian Stations During Peace.

   8. Coordination of the operation of Government radio stations with each other and with the operation of civilian radio stations in time of peace will be governed by the provisions of the radio act of 1927 (secs. 6, 8, and 25).

8. Coordination of Development Program.

   9. The Chief Signal Officer of the Army and the Director of Naval Communications will coordinate the peace-time radio operation and operational development of the two services. The Chief Signal Officer of the Army and the Chief of the Bureau of Engineering of the Navy Department will coordinate their recommendation for the procurement programs of the Army and the Navy and will coordinate technical radio matters of joint concern to the two services.

Approved by the Secretary of War and the Secretary of the Navy June 24, 1927.

Section B
Joint Army and Navy Radiotelegraph Procedure

		Paragraphs
I.	General	1-3
II.	Call up	4-6
III.	Answering the call up	7-9
IV.	Normal form of message	10-19
V.	Procedure signals	20-44
VI.	Control of artillery fire by radio	45-49
VII.	Strength and readability of signal	50-53
VIII.	Z signals	54
	Index	Last page

---

1. General.

   1. Details for intercommunication by radio between the Army and the Navy shall be made by the senior officers of the two services in the area concerned.

   2. Address and signature.

      1. Address and signature codes will not be used between the Army and the Navy.

      2. Messages intended for an addressee on board ship or in a unit of command will be routed by call letters of the station concerned. Delivery to proper officer or office is a function of the command addressed. When believed necessary to secure proper delivery, more complete address may be included in the body of the message.

      3. All official messages will be authenticated in the name of the commanding officer. This signature is not ordinarily transmitted.

3. Use of clear and secret language.

   1. In time of peace, messages are transmitted in clear or in secret language as directed by the writer.

   2. 1. In time of emergency, all messages, except as noted below, are transmitted in secret language.

      2. When the tactical situation is such that time cannot be spared for cryptographing, and when the information to be transmitted if intercepted by the enemy could not be acted upon in time to influence the situation in question, a commanding officer or his authorized representative may order the transmission of a message in plain language by a radio station serving his headquarters.
2. Call Up.

   4. 1. The call up shall consist of the call sign(s) of the receiving station(s) transmitted not more than three times, the letter "V" and the call sign of the calling station transmitted not more than three times. This may be followed by certain signals to indicate the purpose of the call up.

      2. The call up may be:

         1. Single-station, as NA V BA K.

         2. Collective,as DAB DAB DAB V BA BA BA K. DB in this example might be the "net call," in which case all nonsilent stations in the net would answer; or it might be a "group call," in which case all nonsilent stations in a particular preassigned group would answer.

         3. Multiple, as NA NA NB NB V BA K, in which case NA and NB both answer.

         4. General.--The general call for Navy and Marine Corps stations shall be USN, and for Army stations USA. The general call shall be used to establish communication in case the call letters of the station with which communication is desired are not known. Example: USN USN USN V BA K.

   5. In order to avoid undue interference with other communications, the following rules will be observed in calling:

      1. The call signs of the receiving and transmitting stations are made once only except when great distance or poor transmitting conditions make repetition desirable.

2. If the receiving station fails to answer, the first call up may be repeated once.

3. If the second call up is not answered, the transmitting station will wait at least two minutes before repeating the call up.

4. If the receiving station still fails to answer after this further call up, it may be called at intervals, but not more frequently than once in five minutes, except for the transmission of an urgent or priority message,in which case no restriction is placed upon the repetition of the call up.

5. When two stations are known to be within easy radio range of one another, it is unnecessary first to call up such station before sending the message.
6. If the calling station has an urgent or a priority message for the called station it shall indicate that fact by adding the signal O or P to the call up. Example: NA V BA O K.
3. Answering the Call Up.

   7. 1. The station called shall reply by transmitting not more than three times the call sign of the calling station, the letter V, its own call sign, and, if it is ready to receive traffic, the letter K.

      2. A net, group, or general call up requiring an answer is answered by the called stations in the alphabetical order of their call signs; a multiple call up requiring an answer is answered in the order in which the stations were called. If a called station fails to answer in its turn, the next station in the order of answering, after waiting 15 seconds, will answer and the delinquent station will not answer until all other stations have finished.

   8. If the station is busy or is otherwise unable to take the message, it shall replace the letter K in the reply formula by the signal AS followed if desirable by a number indicating in minutes the probable duration of the wait.

   9. 1. If the calling station has indicated that it has an urgent message for the called station, the latter will answer as indicated in (b) below even if by so doing it must interrupt traffic of lower priority.

      2. Example of answering the call up: BA V NA K.

4. Normal Form of Message.

   10. The normal form of message for transmission between Army and Navy stations shall be as follows:

       Part	Example	When used	Para- graph
       Call	NA V BA	Always	11
       Number	NR 3	Usually	12
       Operating instructions		Special cases only	13
       Class		Urgent or priority messages only.	14
       Check	GR 7	Usually	15
       Break	BT	Always	16
       Text	The message in secret or clear language.	do	17
       Time or origin	0923	Usually	18
       Ending signal	AR (followed by K, B, VA, etc.)	Always	19

   11. Call.--The call consists of the call sign(s) of the station(s) called (in alphabetical order), followed by "V" and the call sign of the station calling, each call sign being made once.

   12. Number.--

       1. The message number is a serial number of a separate series, beginning at midnight, for transmission to each station worked and another separate series for reception from each station worked. Thus, since midnight on a certain day BA has transmitted three messages to NA and has received five messages from him. His next message to NA is NR 4 and his next message from NA is NR 6.

       2. The message serial number is a material aid in the handling of traffic. Its primary purpose is to prevent the omission of messages; it is also useful in identifying messages for repetitions, omissions, etc.

       3. The message number may be omitted at the discretion of the transmitting office, which, however, assumes responsibility for any error which may occur thereby. The message number is usually unnecessary in fire control and aircraft work, and in messages consisting

of procedure signals. It may also be omitted in the case described in paragraph 3(b)(2) above.
13. Operating instructions.--Operating instructions are special instructions for operating and for relaying the message when relay is necessary. (See F, par. 27; G, par. 28; T, par. 38.)

14. Class.--

    1. Messages are classified to show the relative order in which they shall be transmitted. This order is as follows:

       Class	Symbol
       Urgent	O
       Priority	P
       Routine	None

    2. The urgent classification is reserved for messages requiring the greatest speed of handling. Urgent messages will be sent immediately upon receipt, except when communication involving another urgent message is being carried on. The urgent classification is used only in combat or when combat is imminent, real or simulated, to indicate that the message following conveys most urgent orders, information or request pertaining to the combat.

    3. The priority classification is used for messages of less urgency than those entitled to urgent classification but of such nature as to warrant precedence over routine messages. Priority messages will be transmitted before such routine messages as may be waiting to be sent but communication of a message will usually not be interrupted to send a priority message.

    4. The routine classification is used for messages which require no special precedence. They are transmitted in the order in which they are received or in such order as will clear the traffic in the shortest time. No signal to indicate routine classification is transmitted.

    5. In the absence of specific instructions to the contrary, messages of the same class, whether they originate in Army or Navy, will be handled in order of filing or of receipt for transmission.

15. Check.--

    1. In plain-language messages, each dictionary word of the test is counted. The writer's message number is counted as one word; the time or origin or any continuous group of letters, numerals, or of letters and numerals is counted as one word.

    2. In code or cipher messages each group of the text, whether numeral, letter, or mixed numerals and letters, is counted, including,

when sent, the writer's message number, the code or cipher indicator, and the time of origin.
3. When a message is to be transferred to or from a communication system which uses a method of word count other than that prescribed in (a) and (b) above, the military or naval office which handles the transfer is responsible that the text of the message is correctly transferred. The check in the other system will be made by the office of that system which first receives the message.

4. The purpose of transmitting the check of a message is to prevent the omission of any word or part of the message.

5. The check may be omitted under the same circumstances as the message serial number. (See par. 12(c).)
16. Break.--The break sign BT will be used to separate the heading from the text of the message.

17. Text.--

    1. The text of the message will be transmitted as written in secret or clear language (without space signs separating the words).

    2. The writer's message number, if given, and the code or cipher indicator, if the message is in secret language, are transmitted in the order named as the first words of the text.

18. Time of origin.--

    1. The time of origin is the time at which the message is signed by the writer, unless the writer fails to note the time on his message, in which case time of origin is the time at which the message is filed at the first message center or communication office through which it passes.

    2. Time of origin is transmitted as a group of four figures, the first two digits representing the hours from midnight and the last two the minutes past the hour. Examples 0600 is 6 a.m.; 1943 is 7.43 p.m.

    3. The time of origin usually appears in official messages. It is not used, however, with messages consisting of--

       1. Procedure signals.

       2. Corrections to messages.

       3. The executive signal.

       4. Messages which are going to be followed by the executive signal.

19. Ending signal.--An ending signal will be used to terminate each transmission and will indicate the transmitting operator's desire with respect to the transmission which is to follow.
5. Procedure signals.

   20. The following procedure signals are prescribed for communication between the Army and Navy:

       Sign	Meaning	Para- graph
       AAA	Blank, representing missing or doubtful portions	21
       AA	All after (to be used in requesting a repetition or verification)	32,34
       AB	All before (to be used in requesting a repetition or verification)	32,34
       AR	End of message	22
       AS	Wait	8,23
       B	There is more to follow	24
       BN	All between (to be used in requesting a repetition or verification)	23,34
       BT	Break, separating heading and text	16
       C	You are correct	25
       E	Error	26
       F	Do not answer	27
       G	Repeat back	28
       GR	Group(s)	29
       HM	Silence	30
       II	Space	31
       IMI	Repeat; I will repeat; interrogatory	32
       INT	Is this correct?	33
       IX	Message following is a preparatory command; not to be carried out until the signal (command) of execution is received	47
       5-second dash	Signal (command) of execution	48
       2-second dash	Salvo mark (battery fired, i.e., on the way)	49
       J	Verify and repeat	34
       K	Go ahead (i.e., answer--an ending signal)	35
       N	Nothing (or not) received	36
       NR	Number	12
       O	Urgent	14
       P	Priority	14

Sign	Meaning	Para- graph
R	Received or readability (according to context)	37,52
S	Signal strength	51
T	Transmit to	38
T or O	Time of origin	39
TOR	Time of receipt	40
U	Radio guard (Navy); net control station (Army)
UO	Negative silence	30
V	From	4,11,38
VA	End of communication; finished (an ending signal)	42
W	Interference	43
WA	Word after (to be used in requesting a repetition or verification)	32,34
X	Static interference	44

AAA
21. AAA is used in conjunction with "ZCL," the groups missed being indicated by AAA. Use is made of this signal when the receiving station is unable to get a repetition.

    Example: BA has sent a message to NA for relay to NB by NA failed to receive two groups and was unable to obtain a repetition from BA. In order not to delay the message, NA sends it to NB as follows:

    NB V NA NR7 NB V BA ZCL GR 11 BT
    NR2 DFC4 JOFX RABU AAA
    RUHG MILZ YSIP AAA XUBO
    1433 AR K.
    AR
22. AR is used at the end of every message. It means: "This is the end of this particular message." It is used at the end of all other transmissions in normal radio procedure which do not conclude with one of the procedure signals "B," "C," or "R." The signal AR is followed by another message or by AS, K, or VA, which signals indicate the operator's desire with respect to the transmission which is to follow. AR may be written thus: +

AS
23. 1. A is an ending signal meaning "wait." It may be used in answer to a call up (see paragraph 8); to stop transmission because part of the message has been missed or because there is interference or other reason requiring delay, or to notify the receiving station that the transmitting station is unable to continue.

    2. The station receiving this signal does not answer.

    3. Whenever a transmitting station has been asked to wait it resumes transmission at the signal "K."
    B
24. 1. B is an ending signal meaning "There is more to follow."

    2. When transmitting a long message, it may be convenient to send it in portions. In order to insure that each portion has been received before proceeding with the next, the letter "B" is made at the end of each portion. Example:
       NA V BA NR3 GR137 BT
       First 50 groups in text I V 50 K
       NA answers: BA V NA R 50 K
       BA continues: NA V VA II Next portion of text.

    3. When a message is sent in portions, the "B" is followed immediately by figures indicating the number of groups thus far transmitted.

    4. Long radio messages in plain language (i.e. press dispatches, etc.) made by ship and shore stations when not broadcasting on schedule and not employing the break system will be sent in portions, each of which will not exceed six minutes' duration.
    C
25. 1. C is an ending signal meaning "You are correct."

    2. It is used in connection with G, INT, and J to signify the correctness of the message or [portion of a message which has been repeated back or the coding of which has been checked and correctly repeated.

       Example: NA, having repeated back correctly a message from BA, which was prefixed with "G," BA transmits: NA V BA C.

EEEEEEEEEE
26. E (ten times).--This signal is used to erase a word or group which has been incorrectly transmitted. Should a station while transmitting a message make a mistake in a word, group, or letter, it must immediately make the "erase" sign; then make the last word or group which was correctly transmitted, and continue the message. The repeat signal (IMT) is not to be made when a mistake is made in transmission. The "erase" signal will be used exclusively to correct these mistakes.
    F
27. F.--
    1. The letter "F" used in the heading signifies "Message following is not to be answered."

    2. When the letter "F" is used in the heading of messages, the groups of the message are invariably to be made through twice.

    3. When the letter "F" is used in the heading, stations are not to ask for repetitions or corrections of the message without the authority of the commanding officer in each case.

    4. The VA sign is always used to indicate the end of a message or series of messages sent by the "F" method.

       Example: BA has a message for NA, but does not wish NA to answer:

       BA makes:
       NA NA V BA BA NR1 NR1 F F GR2 GR2 BI BT
       VOBU VOBU 1235 VA VA
       NA does not answer.
    G
28. 1. The signal "G" used in the heading means "Repeat back." When repeating back or correcting repetitions, the text or groups concerned are made only once, notwithstanding that the original message may have been made twice.

       Example: BA has a message VUBO ABYZ 1010 for NA and wishes the message to be repeated back.

       NA V BA NR1 G GR3 BT VUBO ABYZ 1010 AR K
       NA, having received the message correctly, transmits:
       BA V NA NR1 G GR3 BT VUBO ABYZ 1010 AR K
       BA answers: NA V BA C VA
       NA does not answer.

2. When G occurs in the heading of a long message which is sent in sections,each section is acknowledged by the receiving station by R followed by the number of the last group or word received, as R 50, R 100, etc. When the last portion of the message has been received, the entire message is repeated back.
GR
29. GR.--The group signal followed by a number is used in the heading of a message to signify: "The text contains the number of words or groups indicated." (See par. 15 for check.)
    HM and UO
30. When necessary a station may silence a whole net, certain stations in a net, or all stations on a certain frequency, by use of the silence signal HM. The silence signal is a command and must be obeyed. Its use is confined to those stations in authority such as airplanes and net control stations. It will not be used until other less drastic methods of obtaining order have been tried. It will be annulled as soon as the emergency has ceased to exist.

    Example: (1) PL, an airplane, working in a net whose net call is DAB, wishes to silence the net. PL sends: DAB DAB C PL HM HM HM HM HM HM VA.

    All stations in the net stop transmitting and remain silent. They will not transmit again except to send urgent traffic or to answer a call from the silencing station or the U station until the silence signal is annulled. To annul the silence signal PL sends:

    DAB DAB V PL UO UO UO UO UO UO VA

    NOTE.--A single station may be silenced, and the silence annulled by substituting the station's call sign for the net call of the examples above.

    II
31. The space signal (the letters "II" made separately) is used for the separation of procedure signals or other parts of the transmission when it is feared that confusion of the signals might otherwise result. Space signals are not used to separate the words or groups of the text; they are sometimes useful in the heading of a message or in messages

consisting of procedure signals. A common use of the space signal is shown by the example under B, paragraph 24.
IMI
32. 1. When the reception of a part of a message is doubtful or completely missed, the receiving station may request repetition of the doubtful portion by the use of IMI followed by AA, AB, BN, WA, GR---, or GR--- to GR---, and the doubtful or missing passage.

       Example: BA has transmitted a plain-language message to NA containing the following sentence in the text: "Prepare to sail for Constantinople at ten a.m. Monday twentieth August." NA having entirely missed the word "Constantinople" transmits:

       BA V NA IMI WAS for K.
       BA replies:
       NA V BA WAS for Constantinople K.

    2. Repetition of an entire message may be requested by the use of IMI followed by the number of the message as:
       BA V NA IMI NR6 K.
    INT
33. When the reception of a part of a message is doubtful, the receiving station may question his reception by the use of TNT followed by the questioned word or passage.

    Example: Same as that of 32(a) above except that NAQ has received but is not quite satisfied with the accuracy of the word "Constantinople." He transmits: BA V NA INT for Constantinople K. BA replies NA V BA C K.

    J
34. When the cryptographing office finds difficulty in decryptographing a received message, verification of the cryptographing may be requested of the originator by the use of J followed by AA, AB, BN, WA, GR---, GR--- to GR---, and the passage to be checked. (If the entire message is to be checked, J is simply followed by the number of the message.)

Example: NA has received the following message from BA:
NA V BA NR7 GR14 BT NR2 DFC4 YSIP NAWU LEGT
ERUV LIOP OHIO RAEQ LATU JOFX GISN TUVI
1150 AR.

The cryptographing office at BA checks the encoding, finds "OHIO" erroneously written for "OHIG" and BA transmits:

NA V BA C NR7 GR8 OHIG II OHIG K.
K
35. K is an ending signal meaning "Go ahead"; "answer."
    N
36. 1. When a station does not immediately answer a message which requires an answer or does not proceed with a message after "K" has been made in answer to a call up, the signal "N" may be used. Example: BA calls up NA:
       NA V BA K.

       NA replies:

       BA V NAN K.

       But BA fails to proceed. NA transmits:

       BA V NA N K.

    2. The signal "N" followed by a serial number means "Message NR--has not been received."

       Example: BA V NA N NR16 K.

    R
37. 1. The signal "R" used by itself means "last message" or "last transmission" received. Example: NA having received a transmission from BAS answers BA V NA R. If NA has a message for BA, he follows the "R" by "B" or "ZAR." BA does not answer (unless he desires NA to wait) and NA proceeds to transmit his message.

    2. The signal "R" followed by NR and a serial number means "Message number --- has been received." This form is preferable to

that of (a) above to receipt for a numbered message. Example: BA V NA R NR16 VA. (For use of R to indicate readability of signals see par. 52.)
T
38. The signal "T" is used in the heading and means "Transmit the following to ----------."

    Example: BA has a message for NB, and as he can not communicate directly with NB he sends it to NA for retransmission to NB. BA transmits thus:

    NA V BA NR5 T NB V BA GR2 BT POLP 0845 AR K

    NA having receipted for the message calls NB and being given the "go ahead" signal transmits:

    NB V NA NR10 NB V BA GR2 BT POLP 0845 AR K

    Note that T is omitted when the message is being transmitted to the station of the addressee. Note also that NR5 is BA's number to NA while NR10 is 's number to NB, the number being reassigned in its own series by each relaying station.

    T of O
39. "Time of Origin" is transmitted as a four-figure group, the last word of the message. (See par. 18.) The abbreviation "T of O" is not used in the original message but is employed in conjunction with the signals IMI and INT in connection with repetitions and corrections.
    TOR
40. The "time of receipt" signal, the letters "TOR" made separately (- --- .-.), is used in conjunction with a four-figure group similar in composition to the time or of origin number, to denote the time at which the message is received. It is written TOR.

    The time of receipt is entered in the proper space on the message blank, but is not transmitted except upon request. The time of receipt is entered when the message is received at a station, whether it is received by radio, land line, visual, messenger, telephone, or any other means.

    A message received at station A by messenger at 10.40 a.m. would immediately be noted by the proper person as being received at 1040,

and he would enter on the blank "1040". This message is transmitted by radio to station B at 1045. The operator at B enters on the blank "1045." If the operator at B then sends the same message to station C by land line at 1050, the land line operator enter "1050" in the proper place.

The time of receipt is never used in referring to messages in the same way as is done with serial numbers and the time of origin. The time of receipt is useful in tracing delays.

When transmitted by radio the "time of receipt" signal follows the time of origin. In cases where the radio procedure requires that messages be transmitted twice in succession, the time of receipt signal (when used) follows the last transmission only.

U
41. The signal "U" following a station's call letters indicates that that station is being announced as the net control station (Army) or radio guard (Navy).
    VA
42. VA is an ending signal meaning "end of communication"; "finished." When used, it indicates that the transmitting operator expects no answer, that he believes the series of transmissions completed.
    W
43. 1. The signal "W" by itself signifies "Am being interfered with by other stations." A call signal following W denotes that the interference is being caused by the station indicated. Examples: NA is prevented from receiving a message from BA owing to interference from other ships or stations. NA transmits:

       BA V NA IMI W K

       Again NA is being interfered with by transmissions from NB, NA transmits:

       BA V NA IMI W NB K

    2. Such steps as are possible are taken by the transmitting station to overcome the interference.

X
44. 1. The signal X signifies "Am being interfered with by static." It is used in a manner similar to that of W in the first example, paragraph 43.

    2. It rests with the transmitting station to take such steps as are possible to assist the receiving station (i.e., by changing power, note, or frequency; by sending in portions; or by using "G" in the heading).
5. Control of Artillery Fire by Radio.

   45. An abbreviated form of message is authorized for the exchange of communications controlling or directing the fire of artillery. Its use makes possible the control by fire by radio, when the radio station of the observer and the radio station of the battery are in direct touch. It is practically impossible to relay fire-control messages through linking radio stations. The term "radio station of the battery" is used to indicate the battalion radio station which will be indirect communication with the battery firing, either by voice or telephone:

       Example: NA V BA BT Text AR K.

   46. When the nature of the answer to a fire-control message is such as to clearly indicate that the previous transmission has been received, the "Received" signal "R" need not be transmitted.
       IX
   47. The signal "IX" which is inserted just before BT means "Message following is a preparatory command, and is not to be carried out until the signal of execution is given."

       Example: NA V BA IX BT Text AR K.

       Five-Second Dash
   48. 1. The five-second dash is the signal of execution and means, "Execute the last preparatory command."

       2. It should be sent by the observer only.

       3. It is always preceded by a call and followed by AR. It is never canceled or annulled.

          Example: NA V BA five-second dash r.

4. If the observer desires, he may send the call at any time previous to the five-second dash. He can then keep contact with the battery, by using the "wait" signal AS until in a position to observe, when the five-second dash will be sent.

   Example: NA V BA AS . . . . . . AS . . . . . . AS . . . . . . five-second dash.

Two-Second Dash
49. 1. The two-second dash is the salvo mark, and means "Battery fired" (i.e. "On the way"). This is sent by the operator at the battery radio station just as the battery fires.

    2. It may be followed by a numeral indicating the time of flight of the projectile in seconds.

    3. It is never preceded by a call.

    Example: Upon receiving the five-second dash, command of execution signal (see par. 48), the battery fires and the operator at the battery makes the two-second dash.

6. Strength and Readability of Signal

   50. It may facilitate the transmission of message traffic if a station, which is to work with another, knows the strength and readability of his signal at the other station.

   51. Strength of signal is indicated by the procedure signal "S" (signal strength) followed by an appropriate figure from the table below. The tables may be used also with the procedure signal "X" (static) to indicate strength of static and "W" (interference) to indicate strength of interference.

       1. Very weak, hardly audible.
       2. Moderately weak.
       3. Medium strength.
       4. Moderately strong.
       5. Strong.

          Example: AB V BC S5 K.

   52. Readability of signals is indicated after the procedure signal "R" by means of the table below:

       1. Unreadable.
       2. Poor but readable; plain language twice; code unreadable.
       3. Fair; readable; plain language once, slowly; code twice.

4. Good; readable; plain language or code once.
5. Perfectly readable.

Example: AB V BC S5 II R2 K.

8. Z Signals.

   54. The following signals in addition to the procedure signals listed in paragraph 20 are prescribed for communication between the Army and Navy.:

       Signal	Meaning
       ZAB	Are you in communication by visual with -------?
       ZAD	Am in communication by visual with ------- (through --------.
       ZAF	Are you in communication by radio with --------?
       ZAG	Am in communication by radio with -------- (through --------).
       ZAK	Call me again at -------- (on --------KCS).
       ZAL	Can you hear --------? If so what is his signal strength?
       ZAM	Can hear --------; his signal strength is --------.
       ZAN	Did -------- send anything for me? If so, please repeat.
       ZAO	Following is what -------- sent (at -------- o'clock).
       ZAP	Have (or -------- has) been calling you since -------- (on -------- KCS).
       ZAR	Have -------- messages for -------- (if blanks not filled, means, "Have a message for you").
       ZAU	I (or --------) will call you again as soon as I (he) can (or at -------- o'clock) (on -------- KCS).
       ZAV	-------- is calling you (on -------- KCS).
       ZAW	Inform -------- that I am calling him (on -------- KCS).
       ZAX	Nothing received from -------- (at --------).
       ZAY	Report when you are in communication by visual with --------.
       ZAZ	Report when you are in communications by radio with --------.
       ZBA	Wait, I must shift to copy another station (or --------) but will call you as soon as I can (or at ------- o'clock).
       ZBK	Reception impossible. Send series of six dashes if transmission received or send series of six dots if transmission not received. Send receipt message when communication next established.
       ZBM	Fragments only received (from --------).
       ZBN	Send each message twice. I have difficulty receiving.
       ZBO	Send each message once only. Reception is good.
       ZBP	Send faster.
       ZBQ	Send slower.
       ZBR	Your are missing dots.

Signal	Meaning
ZBU	Your Morse is difficult to read.
ZBV	Reception very bad; send each group -------- twice.
ZBW	Reception exceptionally bad; send each character -------- times.
ZBX	Reception impossible.
ZBY	Accuracy of reception of messages -------- is doubtful.
ZBZ	Are you certain of accuracy of reception of message(s) ________ (or of group(s) -------- in message --------)?
ZCA	Cease listening in for messages from --------.
ZCB	Groups -------- in message -------- should apparently read as follows: --------.
ZCC	Has executive sign (signal of execution) for last message (or for message following --------) been made?
ZCD	Have you received the signal to execute last message?
ZCF	Have you received SOS just made (by --------) (at -------- o'clock)?
ZCG	Listen in for messages from -------- (on -------- KCS).
ZCJ	Message (--------)does not concern you (or --------).
ZCK	Message which you must forwarded was incorrectly transmitted.
ZCL	Message following was incompletely received; groups missed are indicated by the "blank sign" (AAA).
ZCN	Number of groups (in message --------) was --------.
ZCP	Repeat message(s) from -------- (at -------- o'clock).
ZCQ	Reply to message ________ is to be transmitted now.
ZCT	Following is correct version (of message --------).
ZCU	The following is heading of message (--------) as received. Check to origin if necessary and repeat.
ZCV	Transmit your messages in strings of --------.
ZCW	Am going to transmit messages in strings of --------.
ZCX	Have you received my message --------?
ZCZ	Delay was due to fault in my receiving apparatus.
ZDA	Delay was due to fault in my transmitting apparatus.
ZDB	You are causing delay by slowness in answering.
ZDC	You are causing delay by answering out of turn.
ZDD	Request immediate reply to my message.
ZDF	Send receipt for message (--------) when communication next established.
ZDG	Transmit all of your messages one after the other.
ZDH	When may I expect answer to my message --------?
ZDM	Continuous frequency.
ZDN	Vacuum tube transmission.
ZDP	Land wire or cable.
ZDR	Radio telephone.
ZDV	Tonic train (chopped CW) transmission.
ZDW	Visual.
ZDX	Frequency.
ZDY	Type -------- transmitter.

Signal	Meaning
ZDZ	Type -------- receiver.
ZFA	Model -------- receiver.
ZFJ	-------- is radio guard on -------- KCS (net control station for net whose call is --------).
ZFK	Am ready to take over radio guard (to act as net control station).
ZFL	Are you radio guard (net control station) (for --------)?
ZFM	Indicate ships (stations) for which you are radio guard (net control station).
ZFQ	(--------) Act as -------- (until -------- o'clock) (on -------- KCS).
ZFW	Am in your zone. Relay communications for me.
ZFX	Expect to be out of communication for radio until -------- o'clock. Handle radio communication for this ship (station).
ZFZ	Am (or -------- is) unable to --------.
ZGA	Are you (or -------- is) unable to --------?
ZGB	Am going to use (or am shifting to) --------.
ZGC	Am (or -------- is) unable to use --------.
ZGD	Am (or -------- is) using --------.
ZGF	Use --------.
ZGG	My antenna (or antenna of --------) has been damaged (or carried away).
ZGJ	My receiving apparatus is temporarily out of commission.
ZGK	Repairs completed. Am in commission.
ZGL	There appears to be something wrong in your (--------) receiving equipment.
ZGM	There appears to be something wrong in your (--------) transmitter.
ZGN	My -------- (or -------- of --------) is defective.
ZGO	Your -------- appears to be defective.
ZGP	I can not transmit on -------- KCS.
ZGQ	Your antenna appears to be grounding.
ZGR	At the end of this transmission I (or --------) will transmit on CW.
ZGS	I have increased my radiation.
ZGT	My radiation is good.
ZGU	I can not receive (--------).
ZGV	How is my note?
ZGW	Lower your note.
ZGX	Raise your note.
ZGY	Your note is bad.
ZGZ	Your note is clear and musical.
ZJA	Your note is rising and falling.
ZJB	Decrease strength of signals.
ZJC	Increase strength of signals.
ZJD	How are my signals?
ZJF	What is my signal strength?
ZJG	Your signals are unreadable owing to your bad note.
ZJJ	Your spark is broken.
ZJK	Your signals fade.

Signal	Meaning
ZJL	Cease using --------.
ZJM	Act as relay between me and --------.
ZJN	Give me your message for --------; I will forward it.
ZJQ	Inform me when this message (or message --------) has been received by the addressee (or by --------).
ZJR	Message -------- has been received by the addressee (or by --------).
ZJV	Message(s) -------- has (have) been sent by land wire.
ZJY	Take no further action with regard to forwarding message -------- (to --------).
ZJZ	Transmit this message now (or at --------) by "F" method.
ZKA	Transmit this message now (or at --------) without preliminary call up.
ZKC	Transmit this message now (or at --------) by "I" method.
ZKG	Pass following message to destination by dispatch mail system.
ZKH	Distribute this message by dispatch where no charges are involved and to all others by mail.
ZKM	Forward this message by commercial niteletter.
ZKN	Send V's on your present frequency (or -------- KCS).
ZKO	Am going to send V's on my present frequency (or -------- KCS).
ZKP	Am going to transmit on -------- KCS.
ZKQ	Am shifting to receive on -------- KCS.
ZKR	Am (or -------- is) unable to transmit on -------- KCS.
ZKU	Am (or -------- is) transmitting on -------- KCS.
ZKX	On receiving "K" on -------- KCS I shall (or -------- will) transmit message to you on --------KCS. Answer on your present frequency (or -------- KCS).
ZKY	Shift to receive on -------- KCS until further orders.
ZKZ	Shift to -------- KCS.
ZLA	Transmit and receive on -------- KCS.
ZLB	What frequency are you (or is --------) using?
ZLC	How is my frequency?
ZLD	Your frequency appears to be correct.
ZLF	Increase your frequency a trifle (or -------- KCS).
ZLG	Decrease your frequency a trifle (or -------- KCS).
ZLH	Your orientation is wrong; check it immediately.
ZLJ	Transmit on -------- KCS.
ZLK	Shift from telegraph to compensating frequency or vice versa.
ZLL	Check your frequency.
ZLV	General call; all stations copy.
ZMC	Who is interfering with you?
ZMF	I am being interfered with by -------- (on -------- KCS).
ZMG	Listen in before transmitting. You are causing unnecessary interference.
ZMJ	Do not interfere, I am receiving from --------.
ZMK	You are causing interference.
ZML	You are causing interference by inattention to order to wait.

Signal	Meaning
ZMM	You are causing interference. Send on another frequency.
ZMN	You are sending at the same time as --------.
ZNO	Answer -------- and take his message(s).
ZNP	Answer calls for me (or for --------).
ZNU	Answer in alphabetical order of call signs.
ZNV	Answer on -------- KCS.
ZPA	Negative; no; not. (For use with operating signals only.)
ZPB	Affirmative; yes. (For use with operating signals only.)
ZPF	Send -------- (weather, obstruction, storm warnings, press, etc.) Last received (or received at --------) to me (or to --------).
ZPG	Set clocks to --------o'clock upon receiving signal of execution.
ZPH	What time is it?
ZQO	Send report of weather conditions your vicinity.
ZXA	What was station serial number of last message received from this station (or from --------)?
ZXB	Station serial number of last message received from you (or from --------) was --------.
ZXC	What was station serial number of last message you transmitted to me (or to --------)?
ZXD	Station serial number of last message transmitted to you (or to --------) was --------.
ZZO	Broadcast your messages without preliminary call up.
ZZP	Do not broadcast. Call your station first.
ZZX	Close your station.

Index

	Paragraph
AAA	21
AA	32, 34
AB	32, 34
Address	2
Answer	35
Answering call up	7 to 9
AR	22
Artillery fire control	45-49
AS	32, 34
Authentication	2
B	24
Battery fired	49
BN	32, 34
Break	16
BT	16
C	25
Call	11
Call up	4-6
Check	15
Class	14
Code indicator	17
Control of fire	45-49
Correct	25
Correction	26, 28, 32
Cryptograph indicator	17
Dash, two-second	49
Dash, five-second	48
EEEEEEEEEE	26
End of communication	42
Ending signal	19
Erase	26
Execution, command of	48
Executive signal	48
F	27
Finished	42
G	28
Go ahead	35
Group	29
GR	29
Guard, radio	41
HM	30
II	31
IMI	32
INT	33
Interference	43, 44
IX	47
J	34
K	35
Language, clear	3
Language, secret	3
Long messages	24
Missing groups	21
More to follow	24
N	36
Negative silence	30
Net control station	41
Normal form of message	10
Nothing received	36
NR	12
Number	12, 15, 17
Number, writer's	17
O	14
On the way	49
Operating instructions	13
P	14
Press despatches	26
Preparatory command	47
Priority	14

	Paragraph
Procedure signals	20, 54
R	37, 52
Radio guard	41
Readability of signal	52
Received	37
Relay	38
Repeat back	28
Repetition	32
Routine	14
S	51
Salvo mark	49
Signature	2
Silence	30
Silent station	27
Space	31
Static interference	44
Strength of signal	51
T	38
Text	17
Time of origin	18, 39
Time of receipt	40
T of O	39
TOR	40
Transmit to	38
U	41
UO	30
Urgent	14
V	4, 11, 38
VA	42
Verification	33, 34
Verification of cryptographing	34
W	43
WA	32, 34
Wait	23
X	44
Z signals	54

---

Approved by the Acting Secretary of War and the Acting Secretary of the Navy, August 16, 1928.

Table of Contents  *  Previous Chapter (8)

Footnotes:

1. NOTE.--Ch. IX--Communications--is a reprint of ch. VI--Communications, Joint Action of the Army and the Navy, 1927, and is effective until completion of revision now in progress. Paragraph numbering of old Ch. VI is retained pending revision.