SMOOTHING FUNCTION.

T.O. 31W2-2GSC24-2

TM 11-5805-688-14-1

NAVELEX 0967-LP-545-3011

code store. In the frame maintenance mode, each 23-bit

loop arrangement as depicted in simplified form in figure

pattern containing seven or less errors causes the up/

5-9.

Under control of a gated clock (GC) signal

down confidence counter to be incremented by one

generated within the demultiplexer common electronics

count, and the frame sync latch to remain set. Each

section, data bits associated with a given channel are

received code containing more than seven errors causes

read from the serial data bus into the channel card

the up/down confidence counter to be decremented by

elastic storage register. The GC signal exactly matches

one count. If several successive codes containing more

the GC signal applied to the transmitting multiplexer

than seven errors are detected, the confidence counter is

channel card, and therefore may have individual clocks

decremented to 0 and the frame sync latch is reset to a

added or deleted as necessary to accommodate channel

loss-of-frame condition. In such an event, the frame

rate variations applied to the multiplexer's channel input.

acquisition mode is again automatically initiated.

Data in the demultiplexer channel card's elastic storage

5-63. Based upon the above discussion, it can be

a voltage-controlled multivibrator (VCM). Located on the

established that the demultiplexer frame synchronization

channel card, the VCM is configured to operate

function operates in two automatically selected modes:

independent of the GC at the channel's nominal output

acquisition and maintenance. Frame acquisition is

data rate, and also provides the channel's output timing

accomplished by a combined parallel and serial search

signal.

for one of the three overhead stuffing codes transmitted

by the multiplexer. Frame maintenance is achieved by a

5-67. Since there are variations in the rate of the GC

23 bit serial search for one of the three possible codes.

timing signal, the VCM and GC signals are phase locked

In either the acquisition or maintenance mode, a

to prevent underflow or overflow of the elastic storage

prescribed number of detected code errors may be

A phase comparator determines when a

present without causing disruption of the overall frame

predetermined offset between the channel card's input

synchronization process. Further discussion of the

and output counters increases or decreases beyond

frame synchronization function is presented in

acceptable limits. When an unacceptable offset is

paragraphs 5-108 and 5-472.

detected, the phase comparator yields a corresponding

error signal that is routed, via a filter/amplifier network, to

5-64.

SMOOTHING FUNCTION.

the frequency control input of the VCM. Thus, when the

input counter is determined to be operating faster than

5-65. When outputting data other than voice, channel

the output counter, the resultant error signal causes an

cards in the demultiplexer perform a synchronous-to-

increase in the VCM output frequency. In turn, when the

asynchronous buffering process that is the inverse of the

input counter is determined to be operating slower than

stuffing operation performed in the multiplexer. The

the output counter, the resultant error signal causes a

demultiplexer destuffing process results in reinsertion of

decrease in the VCM output frequency. The net effect is

those rate variations that were present at the transmitting

that the input counter and output counter timing sources

multiplexer's channel inputs.

are phase locked. Circuits within the filter/amplifier

network are

5-66. A smoothing function is also accomplished by an

analog

phase-locked

Change 1 5-18