AUTOVON INTERFACE

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.

2-12. AUTOVON INTERFACE

2-2) can be classified as a minor relay station. The

(fig. 2-3)

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

2-11.

objective of AUTOVON is to establish a common-user

(fig. 2-3)

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

2-8