system printouts. The MPD program provides an
additional capability for on-line message composition
and editing ability, and outgoing message error analysis
(before transmission). It also provides a proof copy
with paper tape for off-ship transmission. The (V)2-
MPD system consists of the same equipments as the
(V)2 system with the addition of MPD units, which are
modified video displays.
The NAVMACS (V)3 configuration automates
certain processing functions required in the handling of
narrative messages. It serves as an afloat terminal
within those communications networks using broadcast
and point-to-point modes of operation on both
conventional and satellite transmission paths.
The (V)3 configuration interfaces with up to four
channels of fleet broadcast, and up to four channels of
full-period termination send-and-receive circuits. It
also interfaces with one channel of incoming and
outgoing high-speed satellite link message traffic to and
The (V)3 configuration also interfaces with off-line
torn tape and manual transmit/receive circuits of any
type. The (V)3 system provides the capability of on-
line message composition and on-line message retrieval
fom magnetic tape.
The NAVMACS (V)5/(V)5A system is an
automated communications processing system capable
of interfacing a mix of input/output channels. This
system is enhanced with the addition of remote
terminals for message input. It includes up to four
incoming broadcast channels and eight itinerant, netted,
and fully dedicated communication network channels.
It also includes one incoming/outgoing high-speed
satellite link with CUDIXS and onboard peripheral
The (V)5/(V)5A system includes a remote terminal
capability for direct input/output of narrative and data
pattern messages to high-volume onboard user areas.
Remote terminals consist of a medium-speed printer,
video display, and paper tape reader/punch, or a
combination thereof, depending on the unique
requirements of the various remote terminals.
COMMON USER DIGITAL INFORMATION
The Common User Digital Information Exchange
System (CUDIXS) provides a bidirectional, ship-to-
shore-to-ship, high-speed digital data communications
link between a ship and a NCTAMS or
NAVCOMMTELSTA. Subscriber stations use the
NAVMACS as their terminal. The link consists of a
single Fleet Satellite Communications (FLTSATCOM)
half-duplex channel. The link is dedicated to
synchronous communications between the CUDIXS
shore station (Net Control Station (NCS)) and the
subscribers afloat. Each CUDIXS communications link
can operate with up to 60 subscribers. There are two
types of subscribers: special and primary.
Special subscribers are those ships that are assigned
subscriber identification (SID) numbers 1 through 10.
Special subscribers can send and receive narrative
traffic to and from CUDIXS.
Primary subscribers are assigned SID numbers 11
through 60. Primary subscribers are restricted to a send
capability only. They can receive their shore-to-ship
message traffic via other means, such as the fleet
broadcast or fill-period terminations. Both types of
subscribers can send or receive operator-to-operator
(order wire) messages.
CUDIXS/Subscriber Net Cycle
CUDIXS/subscriber communications are
accomplished through a modified round robin network
discipline. The basic round robin net operating concept
transfers net control from one subscriber to the next on a
prearranged basis, completing one net cycle when each
participating subscriber has transmitted.
In the CUDIXS/subscriber modified round robin
operating concept, transmission timing and scheduling
are determined solely by the CUDIXS shore station
designated the NCS. Each net cycle starts when the
NCS transmits a Sequence Order List (SOL) along with
narrative traffic and operator-to-operator messages.
The SOL specifies the order in which each subscriber
transmits during the next net cycle and the amount of
time allocated each transmission slot. Each subscriber,
in turn, will transmit at a time computed from
information in the SOL.
A net cycle can range from 20 to 120 seconds,
depending upon the amount of transmit time requested
by the subscribers and the amount of data transferred.