TNAG-1940-FCO40-2766-Future-of-Hong-Kong-defence-and-public-order-1989 — Page 64

CONFIDENTIAL

Redacted under FOI Exemption Sec 23/24

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135. Rear Link Communications. Originators should note the following limitations of the two different types of Rear Link circuits and the consequent delays which are likely to occur in the preparation and transmission of certain categories of messages:

a. CRL(S). This provides an on-line RATT and a secure speech channel. Both available normally 24 hours a day. A CRL(S) provides a much better service than a CRL (HF); Top Secret messages, and messages bearing a Special Handling caveat, nevertheless must be off-line encrypted.

CRL (HF). An on-line Radio Teletype (RATT) circuit with the capability of reverting to hand speed morse. Dependant on HF propogation conditions, type of transportable radio station and operating range, circuit could be out for up to a total of 7 hours a day. Top Secret messages, and messages bearing a Special Handling caveat, must be off-line encrypted. This applies also to Secret messages in those plans which require the CRL to work into an Australian anchor station. Should it be necessary to revert to hand-speed morse, all messages classified Restricted and above will have to be off-line encrypted.

SECURITY

136. Security of Part 2 Plans.

a. The circulation of Part 2 plans must be stringently controlled within the countries to which the plans relate. No plan is to be reproduced, fully or in part, without reference to the issuing authority.

b. The level of grading of Part 2 plans will be decided on their merits. The whole plan will be covered by the highest grading within that plan. Telephone reference to a JTP should not couple the number and country or the number and type of plan.

137. Security of Sensitive Message Traffic. Certain messages, particularly in the initial stages of an operation, are likely to contain sensitive national information or to have political implications. Such messages must be safeguarded by the use of the appropriate national caveat or the restricted marking "UK COMMS ONLY" as appropriate. Instructions to originators on the use of these markings are contained in the following single-Service publications:

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CONFIDENTIAL