Magnetic tape messages prepared for transmission
are limited to a maximum of 40,000 characters (five
hundred 80-character data records) that include the
header, text, and EOT records. The preparation of
magnetic tape messages, formats, routing, contents, and
sequence on tape is the responsibility of the message
Message and Tape Reel Accountability
Each tape reel given to the MTTS operator for
transmission must bear a tape label containing the
Number of messages recorded on tape;
Highest precedence used;
Highest security classification;
Date and time filed;
Beginning and ending SSNs; and
Time delivered to the MTTS operator.
Each blank reel of tape furnished to the MTTS
operator for mounting on the receive tape transport
contains a tape label with the following information
recorded in the sequence of handling:
A statement that the reel is blank;
Highest classification ever recorded;
Time the reel is mounted on the receive
Time the reel is removed from the receive
Time the reel is delivered to the addressee; and
Number and types of message on the reel and
other applicable reel information.
All originated tape reels must be retained for at least
10 days. The header and EOT printouts finished the
MTTS operator for both originated and terminated
traffic are maintained as a station communications
record for at least 30 days. Other logs recommended for
MTTS operation are the master station log and the reel
The master station log reflects the current operation
status of the terminal equipments and circuits. This log
should also reflect equipment and circuit outages,
causes of the outages, and the corrective actions
The reel delivery log should indicate the reel
number and the time the reel was delivered to the
transmitting operator or the addressee.
Required security protection must be extended to
all classified traffic transmitted through the AUTODIN.
The ASC automatically checks and compares the
security classification stated in the header of the
message against the authorized security level of the
incoming circuit. Transmission of a message with a
higher security level than authorized will result in the
message being rejected by the ASC.
In addition, an automatic system-generated service
will be transmitted by the ASC to the originating
station. The purpose of this service is to advise the
originating station of possible security compromises.
Also, the ASC automatically checks and compares the
security classification contained in the header of each
message against the security classification of each
destination. A security mismatch occurs for each
destination that does not indicate a matching security
In the event of a security mismatch, the ASC takes
the following actions:
In a single-address message, the ASC rejects the
message and alarms appear at the originating
terminal indicating that the message needs
In a multiple-address message with at least one
deliverable destination, the ASC accepts the
message and delivers it to all valid destinations.
For invalid routing indicators, an automatically
generated service retransmits the message to the
originating routing indicator and advises that the
message needs retransmission.
In-station operating procedures should be carefully
planned and rigidly enforced to prevent inadvertent
transmission of classified messages to unauthorized
stations or agencies. Complete security precautions and
operating rules are contained in JANAP 128.