At the start of World War 2 the government set up an organisation called the Radio Security Service. The aim of this service was to detect and report possible enemy transmissions. The task of selecting suitable volunteers was passed to the Radio Society of Great Britain who then recruited radio amateurs for the task.
  These selected volunteers became known as the Voluntary Interceptors. They (the volunteers) worked from home and they monitored various frequency bands for illegal transmissions. Volunteer Interceptors were not allowed to transmit as all amateurs in England had been closed down under the Defence Regulations.
  It was thanks to the Volunteer Interceptors that the communications network of the Abwehr, the German Secret Intelligence Service was discovered.

  The following has been transcribed from a document held in the museum library. Sadly the document is faded and in places difficult to read and therefore it has been transcribed into a web page for ease of reading.
  As you will see there are a lot of procedural signs mentioned which when written have a bar across the top:- for example AR, BT, CT, etc. The bars have been omitted during the transcription. Also in several instances where accented letters are normally used, especially German, the accents have also been omitted.

- - - - - - - - - - - - - - - -

RADIO SECURITY SERVICE
VOLUNTARY INTERCEPTORS' GENERAL INSTRUCTION NO. 8

NOTES ON PROCEDURE

1. General

  This memorandum does not pretend to cover all the notes which could be written on procedure, but is issued to help operators to get a broad outline of the work.   Practically all radio communication follows some laid down form of procedure. Although the normal commercial radio procedure is general for all countries, the procedure adopted by various fighting services in each country is distinctive. For instance, if the British fighting forces religiously carry out the procedure laid down exclusively for their use, they cannot be confused with any other force and are easily recognised.
  Correct procedure is a definite challenge. Any agent or alien attempting to adopt these procedures to cover up illicit transmissions invariably makes a slip; (it may only be the omission of a single Morse letter or sign) but a mistake which may easily lead to his identification.
  The necessity for logging the various signs in procedure should be obvious. It means the difference between quick and easy recognition of a message and the doubtful surmises following too little information. The need for logging all the various signs cannot be too greatly stressed:

E.G.  VE GYD V LMB

  Means everything to the Intelligence Staff, whereas "LMB calling GYD” conveys little or no information at all. Two important things emerge then:-

   (i) The vital need for logging all procedure as signalled.
   (ii) The ability to recognise the various forms of procedure used.
  In this kind of work, no Morse letter or sign, however small, should be omitted from the log. It is easier to cross out known information than to surmise the unknown.

BRITISH

2. Types of Procedure.

  The procedure laid down for the Army, Navy and Air Force is fixed. Transgression should not be permitted. Unfortunately it is and consequently our work is harder.

The Navy

  A normal call (in wartime) is thus –

VE GYD 2 v RMU AR

  Particular emphasis should be laid on the VE, V and AR. These are standard British procedure signs and are not used collectively by any other nation, and if we find such an entry in an operator's log it is known at once that it is British. Any deviation from the above, such as:

CT GYD2 v RMU AR

Or

VE GYD2 de RMU AR

becomes a suspicious entry at once, and points to the possibility of someone endeavouring to copy the procedure and failing to do so.

  Examples:-

VE GYD2 v RMU AR  (Call)
VE RMU v GYD2 K7 AR  (Answer)
VE GYD2 v RMU BT (-...-) 12579 II (.. ..) 38461 36885 etc

  The II signs are normally used to separate each group, but if communication is very good, these may be omitted. This brings us to the ending of the message which is of as much importance as any other part, and is always a sure means of identifying British units. The end of all British Service transmissions bear a time of origin, such as 1340, 1750, 1222, etc. and comes into the message thus:

38465 II 17216 II 81777 BT 1340 AR

  Whether the message is in code, cypher or plain language, the time of origin is always made. Consequently if an operator picks up the end of a message he can still identify it as British by the time of origin.

  A common form of signal used by the Services is the letter X followed by three figures.

i.e. X267 X291 etc.

(This should not be confused with the letter X mixed with five- figure groups - i.e. 27X12 5X1X3 X210X etc.)

  The Army, Navy and Air Force all use these "X" signals. Apart from variations in call signs, procedure used by Army and Air Force is almost the same as that used by the Navy.
  Air Force call signs usually take the following form:- Letter Figure Letter (X9A) or Figure Letter Letter (2UK). The Army use three letter calls, one letter of which is usually "accented" i.e. KRÖ

  Unfortunately, at present, the Army is not strictly adhering to the laid-down procedure and consequently may lead to some confusion until the positions of the transmitters are plotted.

FRENCH

General

  Since the outbreak of war, little is known of the procedure adopted by the French Services. Very little Naval radio communication is heard, but the Military and Air units must necessarily have increased their volume of traffic. A few characteristic examples of calls, etc. may help, but final deductions as to the identity of these units can only be made after positions have been plotted.

Naval

  The normal French naval callsigns consist of four letters, the first of which is the letter "F". i.e. FABT, FAGR, etc. The naval fixed stations have three letter callsigns, also beginning with the letter "F" as before; i.e. FUB, FUC, etc. To distinguish the call "to" or "from" the procedure sign "de" is always used.

i.e. VV FUB de FABT AR

  It may be assumed that the text of the messages are, in wartime, cypher or code groups, usually of five letters. The end of a French transmission can readily be recognised by the time of origin, for example:

text of message ..... BT 1705/23/11

  Which, as can be seen, not only gives the time, but also the date and month. It is important that, when logging these intercepts, the "de" sign and the time of origin, if heard, should be noted in the log.

Military

  French Military units have various types of calls. A common one is the letter - figure – letter call. i.e. I7G. As the British Air Force also use a similar type of call, the need for logging the "de" sign etc. becomes apparent. In some cases French Military units have been heard using five figure cypher messages, each group separated by the letter "R". This form of transmission is most common to the Russians. Bearings are therefore required to identify suspicious transmissions to avoid confusion.

ITALIAN

  Of all the procedure methods adopted, the Italian is the most easily recognisable, from the interceptor's point of view.

Naval Services

  The call signs of two types:
   (1) Four letter calls, the first two being "IA": i.e. IALT, IABG etc.
   (2) Letter - Letter - Figure' calls; i.e. XR7, 0P9, etc.

  To separate the call "to" and "from", the procedure sign "da" is always used. This is important, as Italy is the only country using this sign for that particular purpose.

The method of call:- VVVV IAFG da IDR AR

(Three letter calls commencing with I are allocated to Italian Naval shore stations).
Answer — VVV IDR da IAFG K
Message - VVV IAFG da IDR BT (Letter) 0 BT 161 14 23 1750 BT
..... Test in plain language ... BT Signature ...

  Note the letter "O" immediately after the call. This is common in all transmissions. It can, however, be added to thus:
   O   Naval Message
   OD  Naval message of importance.
   OCN Private telegram from ship to shore stations.
  When the two letter figure calls are used, cypher groups usually comprise the text of the message.

For example:  VVVV XR2 da UR7 BT O BT 142 XR4 GR 22
17456 78900 21466 81522 92111 64667 22211
21109 67854 10000 22146 14562 79824 11110
21467 58211 72466 55455 66789 20000 14622
164025 GR22

  A pause between groups. At every ten groups the number of the group at that particular place is indicated thus:- 10000, 20000, 50000, 40000, etc.
  The time of origin should also be noted. It consists of the time and date arranged to form a six figure group. In this case Time 1640, Date 23rd. Where the date is a single number such as 2nd, 5rd, 4th, etc. it is made thus:- 164005.
  Transmissions always end with the GR sign followed by the number of groups in the message. It can be seen that no matter what part of a message is first intercepted, the peculiarities of Italian procedure are soon noticed and the origin of the message known.
 emsp;Operating signals are also used. Whereas the British operating signal is the letter "X" followed by three figures, the Italian is the letter "L" followed by three figures.

L302 L484 etc.

  Italian submarines use a special procedure when diving or surfacing. Examples of this are as follows:

(i) VVVV da IAZH BT BASSO ORE 15R30 NR 6 BT IAZH AR

  This is made through three times and indicates submarine is diving at 1530 for six hours.

(ii) VVVV da IAZH BT ALTO ORE 15R30 BT IAZH AR

  Made through three times and indicates submarine sur¬faced at 1530.

  Occasionally, when searching, a ship may be heard sending a series of two letters such as XR XR XR or LS LS LS etc. on various frequencies. This is a normal Italian transmission for frequency test. Transmission of these letters by one ship usually takes five minutes. Upon the expiration of which, another ship transmits the same letters. Various forms of two letters may be expected on frequencies ranging from 3000 to 13000 KC/s.

GERMAN

General

  German transmissions can generally be identified by the pure C.W. transmitters and the good standard of operating, the speed of which is seldom very fast, but all stations and ships seem to adhere to the same speed as that adopted by the Control Station.

Naval

  W/T signalling in the German Navy is cut down to a minimum. Nevertheless, the procedure employed permits of no error or ambiguity. Instructions from shore station to ship and ship to shore station are carried out by the 'Broadcast' method, and throughout these transmissions callsigns are rarely used, in fact the only calls used are those of the fixed German Naval stations.

  For example -

FUL, GVÅ , OÖL, DUF etc.

  All messages transmitted are in four letter code which is used chiefly by the German navy, but also by H.M. Navy (Auxiliary Craft). Procedure, operating and morse keying is of a high standard in ship and shore stations. The transmitters used are such, that to distinguish the transmission of a submarine from that of a shore station is difficult. German Naval stations have fixed routines at each hour and the frequencies employed vary from 3000 to 22000 KC/s. The method of communication is as follows:

  Example: -

    Wilhelmshaven (FUL) has a message for a submarine.
    1920/32 pause 1920/32 pause (A)
     6   pause         (B)
    AEXR     )
    BZRG     )
    FLOR     )          (C)
    DDFO    )
    AEXR    )
    BZRG    )
    VA               (D)

  (A) Particular attention should be paid to this. The 1920 is the time of origin of the message, the /32 is the station series number and is the only means of distinguishing the shore station transmission from that of the submarine.
  (B) The number of groups in the message.
  (C) Four letter code. Slight pause between groups.
  (D) The ending sign.

  Immediately FUL has transmitted this message (Note that no call signs have been used) he requests another station to repeat it, thus:

OÖL al K
(Station 0ÖL repeat back)

  0ÖL then makes the message exactly as FUL originally made it. If repeated correctly the control station simply makes VA (No calls) and this ends the transmission. The submarine reads the message but does not answer. From then onwards until the beginning of another hour, any submarine who has a message to transmit can do so. Except for one small point, the transmission is exactly the same as that employed by the shore station, and it is this point which should be carefully noted. Whereas the shore station always commences his transmission with the time of origin and the series number (1920/32), the submarine makes the time of origin only (1920

STATION	SUBMARINE
1920/32	1920
6	6
AMME	AMME
BGOR	BGOR
KLEF	KLEF
PQEX	PQEX
AMME	AMME
BGOR	BGOR
VA	VA

  It should also be noted that the first two groups of German Naval code are always the same as the last two. If a submarine makes a message, it is intercepted by the shore stations. The control station then asks one of them to repeat the message thus:

GVÄ al 1920
(Station GVÄ repeat message 1920)
GVÄ then repeats and includes a series number thus:
1920/33 etc.

  It can be seen that the German submarines never reveal their call signs, and the stations reduce the use of theirs to a minimum.

German Air

  These are not so secretive in the matter of callsigns. Their calls vary considerably and may be 4 letters (DOZB), 3 letter figure (GY04) or 3 letters (DOH). Calls may be heard thus:

FUL de DOZB AR
or
FUL de GY04 AR

  Messages are usually Five Letter code and thereby distinguish themselves from the naval 4 letter code messages. Procedure is strictly adhered to and operating is of a high standard.

German Military

  The military units also (as in the Navy) conceal their calls as much as possible. Messages are usually 5 letter code and the method of transmitting them very similar to the Naval.

RUSSIAN

General

  At present little is known of the differences in procedure adopted by the various Russian Services, but it is evident that their peculiarities of transmission are the same. The standard of operating in the Russion Services is very poor. Little attention is paid to correct spacing and the formation of letters. The type of call signs used vary considerably and may consist of letters or figures, but never a mixture of the two.

Examples:- ANND BÖRG MchÖR 1249 8813 2614 etc., etc.
ch (----) is a common symbol in Russian calls.

  Nearly all transmissions commence with 'longs', the key being pressed for one or two seconds.

(Call) ---- 'longs' ANND ANND = ALGP
or
'longs' 7631 = 2706

  The BT is always used to separate the calls 'to' and 'from' and makes the call easily recognised as Russian. Almost every part of Russian procedure is divided by the BT sign, but it is noticed that difficulty is often experienced in the making of this sign, frequently being transmitted.
  This method never varies and renders the texts of messages easily recognisable. (There are a few isolated cases where other countries have adopted this method, e.g. French military at times). The Russian, however, is still easily identified by his bad morse and more often than not, his equally bad transmitter. Another sure method of knowing the Russian is by his 'Operating Signals'.
  The British operating signals, for instance, consist of the letter X followed by three figures. The Russian operating signals, however, consist of two letters only, such as .... SH SP MP etc.

  It is characteristic of the Russian to repeat these signals several times ......SH SH SH SH SH SP SP SP etc. etc, and may lead to some confusion if picked up during these transmissions. Russian W/T traffic seems to be on the increase and may be heard on frequencies between 5000 and 8000 Kc/s.

AMERICAN

General

  The standard of operating is good and the transmitters invariably crystal controlled.

Naval

  This Service uses a similar procedure to the British. Stations use their commercial call sign thus:- NAA Washington.
  Ships use their four letter call also beginning with N. Secret calls of the two letter figure type are occasionally used. Procedure signals consist of three letter groups commencing with Z - similar to the Marconi ‘Self evident' circuit code.

  Examples:-

VE NAA V NIDK II T II Z II LARK V NIDK = MESSAGE = 1030 AR
VE YL9 V HL9 GR21 = FRET HYTU JKTY etc = 1230 AR

SPANISH

General

  The standard of operating is very low and the sets used vary from good to bad.

Naval

  Stations and ships use a very distinctive type of procedure, easily recognised. Calls normally used are letter figure letter. Procedure signals are P followed by three figures. Normal communication is by five figure cypher, but plain language and five letter code may be used. An example of the procedure is as follows:

VVVV G7B G7B VVVV P7L P7L NR/135 GR8 = 7CR 7FU = 74321 86542 etc.
VVVV G7B G7B VVVV P7L P7L P130 P176 AR K

COMMERCIAL PROCEDURE

  Commercial Fixed Stations, used on inter-Continental inter- Country Services invariably use a procedure world wide in its application.
  Requests for conditions, strength of signals, acknowledgment of messages, etc. are conveyed to each other by Marconi circuit code, consisting of three letters
ZHC — How conditions?
ZWT — Send words twice, etc.
  Another code called Service Code, used for conveying more detailed information for efficient working of the service and remarks re disposal or non disposal of traffic, consist of five letter pronounceable code, e.g.

DADRO — Listen also .... due congestion
DADXA — Discontinue listen on ....
OKPOD — Please report cause of stoppage to .... hours
TAXAZ to ZAPOG conveys miscellaneous information.

  A transmission of a message in above code can be easily recognised, but it should be clearly understood that this form of code is not exclusive and stations using similar code should be checked.
  Stations situated in isolated parts of the world may be heard on 'fixed' bands using a mixture should he experienced in recognising these stations as they con¬form to recognised methods of transmitting messages.

The Berne publication - "Nomenclature Des Stations Fixes"

  Gives a fairly complete record of stations engaged on these services. Any station heard using call letters allocated to a certain fixed station or wave frequency not allocated to that station, or using definite hand transmissions, should be logged and special attention drawn to it, if he cannot be tied down by the nature of his procedure.

SHIP TO SHORE STATION AND VICE VERSA

  Every country with a Merchant Fleet of any size maintains at least one station on H/P for keeping in touch with their fleet both individually and collectively, for as large a proportion of the twenty-four hours as possible.
  The system generally employed is to have several transmitters on one site calling and answering ships on one or more frequencies, the ships listening to and answering on a frequency most suitable to the geographical position of ship and state of upper atmosphere prevailing at the time.
  Ships and stations use the procedure laid down in the P.M.G. Handbook when calling, and clearing traffic with slight variations according to state of communication. One particular case in regard to stations may cause some difficulty, the following is an example.

CT CQ CQ CQ de GKT GKT
GKT QTC GFAC GFCL GYYM FBHG FBLP OXLA OYUZ WHIM WL EM ANS 18 24 36 54 AR.

  Possibly transmitted by automatic system on several frequencies. This indicates that the station has a message for ships whose call letters are signalled, and these ships are asked to answer on one or other of the bands indicated, i.e.

18 metres (16666 Kc/s) 24 metres (12500 Ec/s)
36 metres (8333 kc/s) or 54 metres (5556 Ec/s).

  If stations are intercepted half way through a transmission of this nature the call signs may be confused with four letter code but the fact that they are alphabetically arranged and the part of the frequency band on which they are heard makes recognition easy.
  These Shore stations also broadcast navigational warnings, press, and repeat S.O.S. messages heard in their areas. Call signs of these stations are as laid down in the Berne list. Gs. Os. and Ws. for Great Britain, Denmark, and America respectively, usually of three letters they can be heard working or idling on their various frequencies almost continually.
  Ships use four letter calls the first letter again indicating its nationality. No strict rule on this point can be made regarding ships of belligerent countries. German vessels have definitely been heard using calls of neutral ships, generally Scandinavian.
  Frequencies used by shipping as previously mentioned {18, 24, 56, and 54 metres) are "mobile" bands in which a fairly large frequency tolerance is admitted. This fact, together with the very wide difference in types of transmitters used on these bands, ranging from very rough I.C.W. to crystal controlled pure C.W. make them eminently suitable for illicit transmissions. Once again, procedure is one means of discriminating between legitimate and illicit stations.

GENERAL SEARCH INFORMATION

  Enclosed is list of unidentified transmissions which have been fairly regular to 12/8/42. When heard on GS please log. Some transmissions are of known group type and are included to guide GS as their callsigns are changed bo work other services as yet unestablished. When call signs, as transmitted, can have alternative meanings,
  Please - note. In the enclosed list, only those stations which come up in our allotted GS bands should be noted.

NOTES ON G.S.

  In order to identify transmissions, as many as possible of the following important facts should be entered on log sheets. Date, time, call, frequency, preamble, type of text, operators remarks and procedure signals, definite operating characteristics which distinguish it from other transmissions.
  A certain amount must be left to your discretion, and as a general rule anything you cannot identify, or feel doubtful about, please log, We will tell you whether it is identified or not.
  There are a certain number of 1, 2, 3 & 4 figure callsigns on various frequencies which have not been identified, and more information is required.
  Transmissions with the following preamble now “wanted” CT 64 wds. 5LC or 5FC. Also any transmission which uses ”T” between calls instead of the usual "de" or ”v” etc.

GENERAL SEARCH INFORMATION No.8

SOME UNIDENTIFIED TRANSMISSIONS

  This edition supersedes all previous editions, and information herein is correct to 25/8/42.
  Fixed and changing callsigns are arranged in the order of frequency applicable to Regional G.S. bands. WHEN THESE TRANSMISSIONS ARE HEARD ON GENERAL SEARCH THEY SHOULD BE LOGGED.
  As soon as any transmission becomes a known Group service or is otherwise classified, logs will be marked accordingly, and on receipt of this information the interceptor need no longer log it on General Search.

SPECIAL NOTE:

  In the case of some entries a figure appears in the "Type” column. This figure denotes the Group to which the transmission belongs, and indicates one of the following:
   (a) that the ANSWER is required
   (b) that this transmitter changes callsign and works an unknown station.
   (c) where both ends are given that either end may change callsign and work other stations.

  Such entries are therefore more nearly a guide to research than a statement that these signals are themselves "suspect”.

Please promulgate quickly.

  In order to identify transmissions, as many as possible of the following IMPORTANT facts should be entered on logsheets Date, time, call, frequency, preamble, type of text, operators remarks and procedure signals, and definite operating characteristics which will help distinguish it from other transmissions.
  A certain amount must be left to your discretion, and as a general rule anything you cannot identify, or is at all doubtful please log. We will tell you whether it is identified or not. Where G.8. band:, can be watched at regular times, daily"suspects” can be more quickly identified, as the majority work to fixed times.
  When callsigns, as transmitted, sound as if they could be read in more than one way, this should be noted.
Many stations after receiving traffic lead one to believe they are signing-off, but in fact, send their traffic three to four minutes afterwards.

  The following are a few items worth noting :
  Unidentified 2,3 an! 4 figure calls are in greater evidence lately. Some transmissions with preamble CT 64 wds - 5LC or 5FC are required.
  Several unusual preambles have been heard lately.
  Suspect transmissions tend, in some cases, to hide under the shadow of powerful transmissions.
  Keep an eye on some identified transmissions and note definite changes.
  Do not be misled by the signal strength of a transmission, Not all suspects are weak.
  Transmissions which APPEAR to have a preamble CT 0542 -142 - 5LC ie, time and letters - are now required. When difficulty is experienced in quoting frequencies, quote your own frequencies AND those of a good marker station close by and state time.

PREAMBLES

  The following preambles precede traffic in which we are interested, but are issued as a glide only, as they are constantly changing. Any preamble which does not adhere strictly to British Service, German Navy and Army, Italian Service or Commercial, should be submitted to us for examination.

Group 1.	(a)	CT  ANXE  BIIAD  LLC  NAX  BT
	(b)	CT  100  BT
	(c)	CT  1360  BT  200  BT  101  BT
	(d)	4 4 3 3 (letters) as in (a) above.	Used by stations whose calls are BLOL; LOL; FPR; RAF
		2 groups
		3 figs
		Sets of 3 figs
- - - - - - - - - - - - - -
Group 2.	(a)	CT  121  BT	(delayed messages CT 2198  121  BT)
	(b)	CT  34/241  BT or Nr 275/46
	(c)	CT  H M * BT
	(d)	CT 58 BT
	(e)	CT L/723 X2 BT
	(f)	CT 49 XZ BT
- - - - - - - - - - - - - -
Group 3.	(a)	CT 03214 78089 137 BT
	(b)	CT 1185 5184 BT
	(c)	CT 12006 .70902 BT
- - - - - - - - - - - - - -
Group 6.	(a)	CT EPNI RNTU PTZ RUEM HHH BT
	(b)	CT 2009 1618 085 HHH BT
	(c)	CT 1618 085 HHH BT
	(d)	CT 085 HHH BT
- - - - - - - - - - - - - -
Group 7	(a)	CT 2009 1615 105 020 222 BT
	(b)	CT 2009 1615 105 020 BT
	(c)	CT 2116 1.953 BT
- - - - - - - - - - - - - -
Group 10.  Same as Group No. 1. only on frequencies 14370 and 14500 K/cs
Group 11  Same as Group 1.
Group 12  Same as Group 1.
Group 13  CT 2109/1516/202 BT STUR BT

Miscellaneous.

OLM Group CT Code 13D 123 26 1500 OLM BT
All letters and figures in the above examples only.

VOLUNTARY INTERCEPTORS’ GENERAL INSTRUCTIONS. No. 9.

Object of the Organisation

  The object is to intercept and locate illicit wireless stations operated either by enemy agents in Great Britain or by persons not necessarily enemy agents operating transmitting stations without being licenced to do so under the Defence Regulations, 1939-
  Note. The term "illicit Wireless Station" includes both traffic passing and radio beacon stations.
  The whole is controlled from Shepherd's Bush 5391 or Acorn 328? by O.C. Radio Security Section (Colonel J.P.G. WORLLEDGE) . The section is subdivided and the Voluntary Interceptor Organisation is controlled by Major Lord Sandhurst , R.Signals. An analysis Bureau under Major E.W.B.Gill, R. Signals deals with logs and Intelligence generally. A control room, (Extension 30) is manned day and night (see paragraph l4)

Voluntary Interceptors' Organisation.

  Voluntary Interceptors are spaced throughout the country and will be controlled by Regional Officers. These Officers will split up their area into Group Leaders who will be responsible for their sub-groups, (see paragraph 60).
  The Interceptors will be asked to furnish logs , daily if possible, but in any case, three times weekly. Information less frequently furnished will, in war time, be of little value.

Role of the Voluntary Interceptors.

  (a) The Interception of il1icit Wireless Transmissions Interceptors are asked to use and extend their knowledge of the local radio "background". This local background will help them, in time, to recognise ground wave signals. Any previous experience they may have had as operators in any of the Services will aid them in recognising the characteristics of stations.
  Interceptors who have been amateur, wireless transmitters can also usefully employ their knowledge of amateur operating conventions and slang; particularly as regards stations abroad. It is most important to remember that a Voluntary Interceptor should not only rely upon what he can pick up on his set, but should also use his ears for local gossip, and his eyes for S„W. aerials etc., particularly any newly erected. In this way, he may hear or see things worth following up.

  (b) Beacons - In the event of an Air Raid Warning being received, watch should be kept immediately, giving special attention to 300 - 1000 metres bands for beacon signals which might be picked up and used by an aeroplane. These may be a steady repeated short code, e.g. single letter or short groups of letters or words, continually repeated, or a string of dots and dashes, or any combination of them, or just a steady note produced by holding down the key, But any unusual signal should be reported.

Communication to the Control Room.

  Cases have occurred when Interceptors have felt bound to communicate to the Control Room, immediately, information of a transmission while it is taking place. On such information, if sent through at once, it may be possible to act and clear the suspicion. As to whether an immediate report is necessary must be left to the individual, who should bear in mind the following points:
  (a) That there will be very few genuine cases,
  (b) That the staff cannot cope with a stream, of such reports, but that if the case is genuine any delay in getting a call through to the Control Room may render the information valueless,
  (c) The telephone call should be made to SHEPHERD'S BUSH 5391 or ACORN 3285 Extension 30, and there only. The name of the operator, to whom the message is dictated should be asked and noted in the log.

Watch Keeping

  Many suggestions (much appreciated and carefully considered) have been made by Voluntary Interceptors as to the frequencies on which watch should be kept, and the possibility of small ranges of frequencies being allotted to the various operators with a view to co-ordinating the intercept system.
  In a more rigid system, this would be possible and desirable, but the role of the Interceptors is individual, is influenced by the leisure available to the operator, and the hours in which he can keep watch, and is complementary to the more regular part of the organisation. Voluntary Interceptors will be advised from time to time the frequencies to be watched. Notes on what to look for are given below in Paragraph. 8 and in V,I, General Instructions No,8.
  The above are general notes. At any time, particular Voluntary Interceptors may be asked to do special interception. On occasion, mobile intercept units of the organisation may be sent to get in touch with Voluntary Interceptors in connection with items recorded in their logs. The personnel will show General Post Office identification cards to establish their identity and should he given every assistance. It may not always he possible to notify Interceptors of such a visit in advance.

Watch Keeping by Groups and Sub-Groups.

  In some districts a group, of sub-groups of Voluntary Interceptors has been formed, and it is hoped to expand this system. Sub-group-working may be either:
  (a) Individuals working with their own sets, but by arrangement keeping watch at different times so as to extend the hours of watch in their locality, and sending in separate logs.
  or
  (b) Two or more operators working with one set only at one of their houses, so extending the hours of watch, and sending in a combined log.

  Groups consist of a small number of sub-groups working together and arranging their watching, so that each sub-group watches a different band of frequencies each 24 hours, thus intensifying the search,

Logs

  Logs should be forwarded in plain envelopes, sealed with the labels provided, to Box No. 485, Howick Place London, S.W.1.
  It will much facilitate the work at the Control Room if the following points are observed:
  (a) Clear handwriting or, if possible, typescript.
  (b) Ink wherever possible. Sharp pencil, if used.
  (c) Use block letters for groups or code, or for any word which is liable to be misread.
  (d) Call signs consisting of mixed figures and letters should be written with the figure half below the line. This obviates confusion between Z and 2, I and 1, etc.
  (e) Keep correspondence separate from logs and put name, date, reference number and town clearly on each. Correspondence is dealt with hy one section here; the analysis of logs by another.
  (f) If your log return is "nil" state periods and wave-lengths over which you listened.
  (g) Will Interceptors please be careful when entering dates and times in their logs?. We hove found, through checking; that dates are sometimes wrong, and it will be helpful if times logged are as near accurate as is possible.
  (8) Traffic which should be logged, (see also V.I.General Instructions No,8 Notes on Procedure),

  Traffic coming under the following headings, if it arouses suspicion, should be logged:
  (a) Communications purporting to be from an amateur transmitter in England. (All amateurs in England have been closed down under the Defence Regulations.)
  (b) Working by Eire amateurs is of interest. They have been closed down.
  (c) American amateurs apparently working to Great Britain, or to enemy countries, may come under suspicion.
  (d) Stations with unusual call-signs should be logged, with sufficient text to help the Control Room to identify them.

Traffic which should not be logged.

(a) Foreign press or broadcasts.
  (b) Foreign language traffic, unless suspected to be on the ground wave,

Last words' on Logs.

  (a) Illegible logs give unnecessary work.
  (b) Logs must be accurate in detail to enable the Control Room to bring their various means of knowledge into play in determining what may be suspicious and worth following up. The individual Interceptor has not access to all these sources.

Administrative.

  (a) Receiving sets supplied are the property of the War Department and are issued on loan.
  (b) Interceptors who have been supplied with receiving sets should report breakages,, repairs, or replacements required to Box 485, and arrangements will he made as necessary. Local radio dealers should not he called in to effect repairs unless instructions are given to that effect.
  (c) Reasonable out-of-pocket expenses for components, batteries, valves, charging, etc. incurred by Interceptors using their own sets will be paid if receipts are fowwarded to Box I+85.
  (d) Cost of trunk calls or telegrams, can only be reimbursed if claimed and if the subject matter is considered to have justified the; expenditure.
  (e) The names of Voluntary Interceptors have been furnished confidentially to Chief Constables of the Police District concerned, for their protection in case of suspicion arising with regard to their watch¬keeping activities.
  (f) Voluntary Interceptors are authorised to state in reply to bona fide official enquiries, that they are engaged in work for the War Office, Box 485, etc, but Officers’ names should not be mentioned,

(signed), Colonel, Radio Security Section, 9, LEIGHTON TERRACE, EXETER.

TO: ALL V.I’s.

  It will be- realised that, now that the War in Europe is over, it cannot be expected that we shall bo able to get the same number of V.l's prepared to put in a regular worth-while period of time in each week to keep the Organisation in its present form. It is obvious, in fact, that we have got to go back to the system under which V.Iery started, and also to the time when V.I's were all run from one central Office. In those days Lord Sandhurst was, in the main, in charge in London and he has now promised to come back .as Lord High V.I, (in a civilian capacity) and help as best he can in keeping the service going. Those who have been V.I's long: enough will remember one point which he continually reiterated - that - the end of the War would be the time when V.I's would really come into their own and have to do. the job for which they were designed. There is' no doubt at all that the truth of these words is now 'being proved; it is becoming absolutely essential that V.I's should do the job for which they were originally intended, namely,.the discovery of the illicit transmitter in this country - in other words "police the ether" This can only be done by V.I's who are prepared to do a regular amount of work. After serious discussion, it has been agreed that, the minimum useful time is 4 periods of 1 hour each week. It is realised that this is asking a very considerable sacrifice from everybody who undertakes it and not only from him, but in the case of the married man, from his "Wireless Widow'.
  It does not demand much imagination to appreciate the seriousness of the situation which would arise if illicit transmission got out of hand through foreign nationals being; scattered about Europe with transmitters ’which they have scrounged or otherwise obtained. It has now been decided that Regional Offices are to be closed, and administration be conducted for .all V.I's from one central point. The object of this letter is to discover the V.I's who would be willing to continuc as such for a further period of 6 months after the closing of the Regional Office, which will occur .at the end of September next. It must be pointed out that the individual will remain a VOLUNTARY INTERCEPTOR, and no monetary inducements can be offered to influence him. If you are willing to continue, will you please sign the form below and return to this office immediately.

Captain, SAX Regjional Officer, S.C.U.3
S.C.U.3.
25th June 1945. DHH/CEP.