5 FEB.]

SHIP-TO-SHORE H.F. COMMUNICATION

Schedule B
Watch is maintained as follows at Area Receiving Stations for Calls from Ships:

SUPPLEMENTARY RECEIVING STATIONS

The following stations are linked to the GBMS Organization. They should not normally be called direct nor have messages addressed to them, but they may offer to accept ship-shore H.F. traffic in order to expedite clearance:

• May to September only. From October to May, change takes place at 1800.

Authority.—Admiralty. (H. 6069/52.)
Wellington, N.Z., 26 January, 1952.
W. C. SMITH, Secretary for Marine.

(M. 10/145)

Notice to Mariners No. 3 of 1953

(This notice repeats parts of Admiralty Notice to Mariners No. 3B of 1953)

3B. OFFICIAL RADIO MESSAGES TO MERCHANT SHIPS — THE MERCAS T SYSTEM.

Former Notice 3B/52 cancelled.

NOTE.--The substance of this Notice will not be reproduced in Admiralty Lists of Radio Signals or in Notices to Ship Wireless Stations.

Amendments will be published weekly in Section VI of Weekly Complete Editions, Admiralty Notices to Mariners (Corrections to Admiralty Lists of Radio Signals and Notices to Mariners 3, 3A and 3B).

IT IS IMPORTANT THAT MASTERS ENSURE THAT THIS NOTICE IS AVAILABLE TO AND UNDERSTOOD BY THEIR RADIO OFFICERS. AN EXTRA COPY IS SUPPLIED FOR THE USE OF RADIO OFFICERS.

GENERAL

This Notice describes an alternative organization to that described in Notice to Mariners 3 whereby official messages can be passed to Merchant ships.

2. This organization is known as the MERCAS T System and will not be brought into force until so ordered by the Admiralty. It is an expansion of the GBMS organization which it would supersede, and provides for fuller world-wide coverage.

3. Each Area is covered by one High-powered shore Radio Station which broadcasts on low and/or high frequencies simultaneously on fixed schedules. Medium-power short range coastal radio stations also broadcast MERCAS T messages to ships estimated to be within range. The initial call on 500 kcs will be followed by the operating signal directing a shift to the working frequency. After a brief interval the message will be broadcast. Messages will be broadcast immediately on receipt and will be repeated at the next single-operator period.

Details of special routines for United Kingdom 500 kcs Coastal Stations will be found under Area IV.

4. Details of the numbered MERCAS T areas and particulars of the participating areas and coastal stations are shown later in this Order. Fuller details of the radio organization will be contained in a publication which will be issued to Merchant Ships when necessary.

LE TTERED MESSAGES

5. General Messages issued by the Admiralty intended for Merchant Ships in all areas world-wide are identified by the word MERCAS T followed by double letters in alphabetical sequence, e.g. :

AA — AZ
BA — BZ
contained in the text.

In addition to these world-wide General Messages there are two other series of general messages. One is applicable to Merchant Ships in the Atlantic Ocean area only, and the other to Merchant Ships in the Pacific area only. These are known as the MERCAS TLANT and MERCAS TPAC Series respectively. These series are identified in the same manner as the world-wide series except that the letters will be prefixed by 'MERCAS TLANT' and 'MERCAS TPAC' as appropriate. Those messages which are not of an emergency or urgent nature will be disseminated to Naval Authorities who will deliver them to Masters upon arrival in port. Such general messages will contain the same identifying features as if they had been broadcast. When a MERCAS T lettered message has been sent to the Naval Authorities for delivery the next MERCAS T general message broadcast to ships at sea will contain information to this effect and indicate the identifying letters of such message. Merchant ships will thus be able to determine whether they have received all messages in each series.

CALL SIGNS

6. Collective call signs to which general messages concerning British ships will be addressed, are as follows :

NUKO … All ships guarding MERCAS T.
NRMS … All Allied Merchant Ships.
NRMS 1 to 13 … All Allied Merchant Ships in Area indicated.
GBMS … All British Merchant Ships.
GBMS 1 to 13 … All British Merchant Ships in Area indicated.
Areas are those shown in the diagram attached; e.g. NRMS 3 … All Allied Merchant Ships in Mercas t Area III.