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STATUS heading on the front panel of the unit. This will tell the user
that the unit has detected a frame error.
FAS Bit Errors
FAS bit errors are detected or inserted into the frame alignment signal
(FAS). They will appear every even frame from frame 0 to 15 in time slot
0.
E Bit Errors
The CRC MFAS is a 6 digit signal of 0 0 1 0 1 0 1 1 and is inserted bit-
by-bit into the first bit of the NFAS in frames 1, 3, 5, 7, 9 and 11. The
first bits of frame 13 and 15 are called E bits and are used to indicate the
data blocks with bit errors back to the transmitting side. If the E bit in
frame 13 = 0 it indicates that there is a CRC error in the data contained
in sub-multiframe I and if the E bit in frame 15 = 0 it indicates the same
situation for sub-multiframe II.
Bipolar Violation Errors & BPV Rate
The BPV error rate is calculated as follows:
BPV Error Rate = BPV Errors / # Total of Bits Received
This parameter is also a good measure for overall quality of service or
health of the E1 link. This is a measurement of the rate at which bipolar
violations are occurring over the entire E1 receive bit stream.
Bit Errors & Bit Error Rate
The BERT-20E1 must be synchronized with a test pattern before it can
detect and record a bit error. Therefore, bit errors are registered only if a
BERT pattern is present. You can determine if the BERT-20E1 has
achieved pattern synchronization by observing the green PATTERN
SYNC LED under the RX STATUS heading on the front panel of the unit.
Each time the test set detects an error in the logic bit stream, one bit
error is recorded. If a bit error is detected, the unit will sound an
The display RESULTS arrow keys are
used to select a SUMRY (summary)
list of error results, NORM (normal)
standard list of BER results, or the
PERF (ITU performance) set of
results. The green LEDs to the left of
the LCD illuminate to indicate that
the corresponding set of results is
currently being displayed on the first
(two) lines of the LCD Display.
When the Display key is scrolled to
SUMRY, a list of BER results may be
viewed on the first (two) lines of the
LCD Display. Utilizing the RESULTS
up and down arrow keys the user
can scroll to the results that caused
the error. The red test summary
LED, located in the RX STATUS
section of the front panel,
illuminates when a bit error, BPV
error, FAS error, E-Bit error, CRC error, or E1 frequency deviation error is
detected.
NORM – Normal List of BER and Non-BER Results
CRC Errors/CRC Error Rate
If the BERT-20E1 establishes frame synchronization with a PCM30C or
PCM31C framed signal, it will detect and record cyclic redundancy
Check (CRC) errors. CRC Errors are recorded if the E1 signal is live
traffic or a BER pattern. If a frame error is detected, the unit will sound
an audible alarm and blink the red test summary LED under the RX
VIEWING TEST RESULTS
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