Advise the connected ASC by routine service
message if only one transmission can be
An ASC receiving notification of a duplicate
transmission should search its records to determine if
the message was received in duplicate. If the message
was not received in duplicate, it must be traced on a
station-to-station basis to determine the point of
Magnetic Tape Messages
Magnetic tape is one of the principal media used in
electronic data processing equipments (EDPEs).
Magnetic tape terminal stations (MTTSs) in the
AUTODIN provide for the rapid exchange of large
volumes of data in a relatively short period of time. The
basic mode of MTTS operation with other AUTODIN
tributary stations is either full duplex or on a store-and-
In the continental United States, terminals that have
compatible equipment and circuit speeds and are
connected to the same ASC may communicate directly
by Hybrid AUTODIN Red Patch Service (HARPS).
HARPS provides a direct subscriber-to-subscriber
encrypted circuit. HARPS uses the same circuit and
equipment normally used in the message-switching
component of the network. Communications centers
not serviced by HARPS communicate by normal
message switching, which automatically performs the
necessary speed, format, and code conversions.
All received tape reels must be periodically
dismounted and made available for delivery as
scheduled by a receiving activity and system manager.
A magnetic tape reel accepted by a communications
facility for transmission is screened and arranged for
transmission according to majority message
precedence levels contained on the reel. Establishment
of transmission schedules is the responsibility of the
commands concerned. Prior coordination is necessary
to provide for efficient use of the equipment and circuit
time. Schedules are limited to 30 minutes per period.
Most facilities establish their own procedures for
maintaining reel accountability and ensuring that
message transmission has been accomplished.
Message header and EOT printouts are finished by the
message originator with each reel of tape to be
transmitted. If a message cannot be transmitted, the
MTTS operator returns the reel to the originator,
identifying the message (or messages) that could not be
sent. The originator is also provided the reason for the
nontransmission, if known.
Terminal equipment should not be used to change
message media format for customer convenience; for
example, changing from magnetic tape to narrative
Communications station master records, such as
history tapes and journal records, remain with the
communications facility until destroyed. History tapes
are labeled to prevent them from being inadvertently
delivered to addressees with live traffic tapes.
Recorded information is very close to the edge of
the tape. Tape-edge indentations, caused by careless
tape handling, will seriously affect the accuracy of
magnetic tape recordings. You should be aware that
tape splices are not permitted in reels of tape used for
Message formats used within the AUTODIN
require that each message contain a message heading,
text, and EOT record. The textual material on magnetic
tapes may consist of a wide variety of information
recorded in either structured or nonstructured formats,
depending upon the type of system.
EOT is either a single N or four consecutive Ns.
The header, text, and EOT cards of magnetic tape
messages are always transmitted in the AUTODIN
common language code (ASCII). This is accomplished
by automatic code conversion logic provided in the
magnetic tape terminal.
The text of magnetic tape messages can be prepared
by the EDPE system in 80-character data images, series
record images, or by variable-length record images.
The length of data records to be transmitted by
AUTODIN may vary according to user requirements.
For general transmission of data throughout the system,
computerized terminals must be capable of transmitting
records that contain from 18 to 1,200 characters.
Subscribers desiring to transmit messages that
contain fewer than 18 or more than 1,200 characters
must ensure that the addressee is capable of receiving
such records prior to transmission. Typical line formats
of magnetic tape message records are described in