Functional Description of Teletype Processing System

b. The data at the signal entry panels can be digital

Function to be converted into a pulse coded modulated

baseband, TTY, and/or VF.

(PCM) format suitable to be applied to the input of the

c. The TTY inputs are applied to the TTY

Multiplexer/Modem functions. Since the Multiplexer used

processing functions where they are prepared for

in the Multiplexer/Modem functions is only capable of

interfacing with the input of the Multiplexer/Modem

providing up to 1.544 Mb/s on its output, the 10 Mb/s

Functions. The TTY processing functions are capable of

data line bypasses the multiplexer and is applied directly

processing up to nine full duplex TTY channels of which

to the modem. This direct path to the modem provides a

five must be externally generated FSK TTY.

Of the

means of transmitting any externally multiplexed PCM

remaining four channels, three can be high level TTY

data stream up to 9.9999 Mb/s (10 Mb/s). When

which is first changed to low level TTY before being

receiving data, the processes described above are

converted to FSK for interfacing with the input of the

reversed in order that each field user is provided with the

Multiplexer/Modem functions. The remaining channel

proper data rate and format.

f. The Multiplexer/Modem functions are used to

can only be used to convert a low level TTY signal to

FSK. If any of the three high level TTY input channels

convert the various digital baseband, VF, and TTY data

are not being used to process high level TTY, they can

streams into a 70-MHz IF, biphase, or quadraphase shift

be used for low level TTY inputs. The nine processed

keyed data stream required by the input of the RSS to

TTY channels are fed through a nine channel filter bridge

prepare it for final transmission to the satellite. Other

which forms them into a single stream to be fed into one

than externally multiplexed data rate input, the

VF channel of the Multiplexer/Modem functions. On the

Multiplexer/Modem

functions

can

process

any

receive part of the CSS operation, the output from the

combination of TTY, VF, and digital baseband channels

Multiplexer/ Modem functions is fed back through the

not to exceed 24 channels, including one for the

TTY Processing Unit, reversing the process described

orderwire. The combined data rate of the multiplexed 24

above, to provide the TTY field users with the

channels cannot exceed 1.544 Mb/ s.

The

appropriate TTY format compatible with their teletype

Multiplexer/Modem

functions

include

system.

encoder/decoder for error correction. Also encryption

d. Up to 12 VF channels can be processed in the

equipment is provided to prevent any change in message

CSS. The VF channels can either be two-wire or

traffic level from being detected.

g. The signal entry panels are equipped with

fourwire service. In the VF processing function, the

signals coming from or going to the field users are

Electromagnetic Pulse (EMP) protectors for protection

adjusted to a 0 dBm level. The four wire channels can

against the combination of electric and magnetic fields

either use 1600-Hz or 2400-Hz frequencies for signaling

produced by an exoatmospheric nuclear detonation.

purposes and the two-wire uses a 20-Hz frequency. The

Such detonation creates an extremely high energy RF

signaling units and ringdown converters detect and

pulse of duration on the order Of 250 nanoseconds and

translate the signaling frequencies into transmit (M) and

rise time of 5KV/nanosecond. The electric field strength

receive (E) signals. the M signals are sent to the

can be on the order of 100,000 volts/meter. In addition,

Multiplexer/Modem functions for transmission with their

interior bulkhead connectors are employed which include

assigned bit stream on a timed shared basis with the

radio frequency interference suppression and series

framing information.

The

two-wire

service

element fuse protectors.

h. The CSS contains an orderwire and a standard

converted to four-wire transmitting and back to two-wire

for the user upon receiving. The 12 VF channels are fed

telephone which can be connected into a local telephone

through echo suppressors before being sent to the

system. Entry panel connectors for patching a 5-MHz

Multiplexer/Modem functions for transmitting.

standard, and 70/700-MHz auxiliary inputs to the RSS

e. The CSS is also capable of processing

are provided. The CSS also has entry panel connectors

baseband digital data inputs from field users. The data

to accommodate four additional four-wire inputs from

channels available are four 20 kb/s, two hybrid 50 kb/s,

miscellaneous VF users.

i. Test equipment is provided to monitor the

256 kb/s or 512 kb/s, and a channel for externally

multiplexed data up to 9.9999 Mb/s (10 Mb/s). The 20

operation of some equipment in the CSS.

kb/s and 256/512 kb/s channels are in a format that

permits them to interface directly into the input of the

2-3.

Functional

Description

Teletype

Mutiplexer/Modem functions. The two hybrid 50 Kb/s

Processing System

channels which have been externally encrypted for voice

a. The Teletype (TTY) Processing System's

secure transmissions (scrambled) must pass through the

Simplified Diagram is shown in figure 2-2.

internal

Digital

Baseband

Processing

2-3