46
MODULAR MODEM ELIMINATOR
transmitted. Other conditions of interest are multiplexed 64-kbps channels
transferred by digital multiplexors.
When the digital multiplexors are synchronized by secondary atomic clocks,
the expected worst-case clock rate difference is approximately 3 x 10
-10
. In this case,
the slippage rate achieved by the Modular Modem Eliminator is given by:
Slippage Rate = 64 x 10
3
x 3 x 10
-10
x 1/128=1.5 x 10
-7
bits/second
This is equal to one slippage every 1851 hours, or one slippage every two
and half months.
When making accurate calculations of bit slippage, additional second-order
effects must be taken into consideration, namely low-frequency clock jitter (clock
“wander”). The clock wander usually does not exceed a peak value of several bit
intervals. Therefore, this is only a small fraction of the Modem Eliminator buffer
size and does not significantly change the slippage rate.
Summary of Contents for ME260A
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