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TM 11-5895-1012-10
matic switching between them.
station is located at the junction of Government owned
b. Automatic Message Relay Centers. There is no
Systems #1, #2, and #3 of the world-wide network, and
need for operator intervention during normal op-
is also an access point to leased circuits carried over a
eration of this type of message relay center. Messages
commercial facility, and a Government owned satellite
am automatically passed, via cross office equipment
system. Signals entering ABC on System #3, as an
from the receiving machine to the transmitting posi-
example, from tributary station LMN or beyond DCS
tion, renumbered and retransmitted to the next relay
Station XYZ, and not destined for a connected tribu-
center or to the addressee. This permits rapid relay of
tary station, would be switched to leave the nodal
messages through the relay center. Delay is only de-
point on Government System #1 or #2, the commercial
pendent upon the speed at which the cross-office
facility, or the Government satellite system. The
equipment operates. So that this facility can operate at
switching can be accomplished on a channel, group or
maximum speed and efficiency, there is a need to
supergroup level. DCS Station ABC provides many
maintain precise accuracy in the production of the
routing capabilities for signals originating at an associ-
original message tape, and high quality of the DCS cir-
ated tributary station, including interconnection of
cuits over which the message travels.
users located at any of the serviced tributary stations.
(2) Minor Relay Station. DCS Station XYZ (fig.
2-2) can be classified as a minor relay station. The
amount of installed equipment would be much less
a. The worldwide DCS main-line trunk routes pm
than that of DCS Station ABC since it is not at a nodal
vide the transmission path for voice frequency com-
point. It services only one tributary station, and pro-
munications over the Automatic Voice Network
vides access only to the East or West on System #3.
(AUTOVON) another DCS subsystem. The basic
Message Relay Center Interface
objective of AUTOVON is to establish a common-user
automatic switching network that provides worldwide
It is not feasible (economically or practically) to have
compatibility, reliability, flexibility, and greater sur-
each teletypewriter user connected directly to every
vivability of telephone communications. The voice
other users machine. Economic interconnection is es-
communications capability is provided between De-
tablished through a complex subsystem network of
partment of Defense users and between Department of
message relay centers. The worldwide DCS is used as
Defense users and certain non-DoD users. The system
the vehicle to transmit messages from one user to an-
is established primarily for voice communications, but
other. Individual teletypewriter signals are multi-
it is capable of handling graphic and data transmis-
plexed into composite signals which are then trans-
sions on a user-to-user basis. It is capable of handling
mitted over the DCS system voice channels. So that
secure communications when the appropriate equip-
every teletypewriter user can transmit to any other
ment is installed at user locations. For operational and
user, a system of message relay centers has been estab-
control purposes, the AUTOVON switch has a built-in
lished to switch (or relay) the messages from one sys-
TCF which functions as a tributary station to a DCS
tem to another and move it from the originator to the
major or minor relay station.
addressee as quickly as possible. The message relay
b. The Automatic Voice Network is intended to
center may be an activity serviced by a tributary sta-
offer identical services worldwide to its users. Services
tion or a tributary station itself. Message relay centers
that are available to users system wide are as follows:
are classified into three categories: manual, semiauto-
(1) Normal Service. It provides the capability for
matic, and automatic.
direct dialing from one user to another on a worldwide
a Manual and Semiautomatic Message Relay Cen-
basis. In instances where limited trunking facilities
ters. The manual and semiautomatic message relay
are available, the user will place the call through a
centers employ the torn tape method of operation. An
local operator or a Dial Service Assistant.
operator tears the incoming message tape off of a re-
(2) Four-Wire Service. Selected subscribers to
ceiving machine, reads the routing indicator, and hand
AUTOVON are provided with a special I-wire tele-
carries it to the transmitting position. This is a rela-
phone for direct access to the network. Data
tively slow method since the speed of passing a
subscribers are provided access to specially condition-
ge tape through the office is dependent upon the
ed AUTOVON data circuits. The signalling from a 4-
and accuracy of the operator in reading the rout+
wire instrument is dual-tone, multifrequency. The
ing indicator, carrying it to the transmitting position,
four-wire service subscribers can also be provided with
and preparing it for retransmission. The semiauto-
up to three levels of precedence for pre-emption of
matic message relay center speeds up the retransmis-
lower level precedence calls when necessary.
sion process by having an automatic numbering proc-
(3) Off-Hook Service. The off-hook service sub
ess and tandem transmitter distributors with auto-
scriber is immediately connected through the network

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