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T.O. 31W2-2GSC24-2
TM 11-5805-688-14-1
NAVELEX 0967-LP-545-3011
subsequent destuffing and smoothing operations, it is
which the 23-bit stuffing code applies, and also enable
necessary to identify the multiplexer port with which the
presetting of demultiplexer minor frame and word
23 bit stuff code is associated. The 5-bit port number
counters. The 29th overhead bit conveys the sense of
information is inserted in bit positions 24 through 28 of
the data bit read from a channel card's data storage
the overhead word. Upon decoding by the demultiplexer,
register when a positive stuffing operation has been
the  port  number  permits  proper  presetting  of
performed by the multiplexer.
demultiplexer minor frame and word counters. Having
detected and decoded the first 28 bits of the overhead
5-19.
MULTIPLEXER BASIC CONCEPTS.
word, the demultiplexer is fully synchronized with the
5-20.
INTRODUCTION.
transmitting multiplexer and is informed of the type of
destuffing it must perform and the port to which the
5-21.  Like  most  time  division  multiplexers,  the
destuffing operation applies.
AN/GSC-24(V) design is structured about the use of
ports for the combining of applied channel inputs into a
5-17
When performing a positive stuffing operation
single interleaved serial output data stream.  Simply
(indicated by the first 23 bits of the overhead word), the
stated, a port is an interval of time during which data
multiplexer issues an extra gated clock to the port
from a particular channel are allowed into the output
identified in overhead bit positions 24 through 28. The
stream. The rate at which the porting occurs is termed
clock forces a data bit from the elastic data storage
register located on the channel card with which the
the port rate (Rp); once established for a given
indicated port is associated.  Since this data bit is
multiplexer set configuration, the port rate remains
actually one bit of channel data, its sense (1 or 0) must
constant for all ports in use.
be conveyed to the demultiplexer for use in subsequent
destuffing operations. Sense of this data bit is inserted
5-22
To enable the multiplexer to simultaneously
into bit position 29 of the multiplexer's overhead word.
accept input channels of different (mixed) rates, multiple
Because no action and negative stuffing operations
ports are assigned to a single input channel. This
performed by the multiplexer do not force a data bit from
arrangement is termed port strapping. The total number
a multiplexer channel card storage register, sense of
of ports assigned to a particular channel may vary
overhead bit 29 is of no significance to the demultiplexer
between 1 and 25, and the variable is designated as K.
when the two stuffing codes are received.
The total number of ports assigned to all input channels
of a given configuration is simply the sum of all individual
5-18.  In  summary,  a  29-bit  overhead  word  is
channel K values, and is designated as N.
interleaved into each minor frame transmitted by the
multiplexer. The first 23 bits of the word enable initial
5-23.  In addition to the total number of ports assigned
frame synchronization of the receiving demultiplexer and
to channels in a particular configuration (N), one
inform the demultiplexer of the type of stuffing action
additional port is always used within the multiplexer for
(positive, negative, or no-action) taken by the multiplexer.
the insertion of overhead data into the output bit stream.
The next five overhead bits (24-28) identify the port to
Generated internal to the multiplexer, the overhead data
include a synchronization pattern for use by the receiving
Change 1 5-5

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