XRT73L04A
4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. 2.0.3
41
When the XRT73L04A is operating in the E3 Mode, a
given channel declares an LOS Condition if its re-
ceive line signal amplitude drops to -35dB or below.
Further, the channel clears the LOS Condition if its
receive line signal amplitude rises back to -15dB or
above. Figure 27 illustrates the signal levels at which
each channel of the XRT73L04A declares and clears
LOS.
Timing Requirements associated with Declaring
and Clearing the LOS Indicator
The XRT73L04A was designed to meet the ITU-T
G.775 specification timing requirements for declaring
and clearing the LOS indicator. In particular, a chan-
nel declares an LOS between 10 and 255 UI (or E3
bit-periods) after the actual time the LOS condition
occurred. Further, the channel clears the LOS indica-
tor within 10 to 255 UI after restoration of the incom-
ing line signal. Figure 28 illustrates the LOS Declara-
tion and Clearance behavior in response to the Loss
of Signal event and then the restoration of the signal.
F
IGURE
27. T
HE
S
IGNAL
L
EVELS
THAT
THE
XRT73L04A
DECLARES
AND
CLEARS
LOS
0 dB
-12 dB
-15dB
-35dB
Maximum Cable Loss for E3
LOS Signal Must be Declared
LOS Signal Must be Cleared
LOS Signal may be Cleared or Declared
