XRT73L04B
4 CHANNEL DS3/E3/STS-1 LINE INTERFACE UNIT
REV. 1.0.1
41
3.5.2
The LOS Declaration/Clearance Criteria
for DS3 and STS-1 Applications
When the XRT73L04B is operating in the DS3 or
STS-1 Mode, then each channel declares and clears
LOS based upon the following two criteria.
• Analog LOS (ALOS) Declaration/Clearance Crite-
ria
• Digital LOS (DLOS) Declaration/Clearance Crite-
ria
In the DS3 Mode, the LOS output (RLOS) is simply
the logical "OR" of the ALOS and DLOS states.
1. The Analog LOS (ALOS) Declaration/Clearance
Criteria
A channel declares an Analog LOS (ALOS_(n)) Con-
dition if the amplitude of the incoming line signal
drops below a specific amplitude as defined by the
voltage at the LOSTHR input pin, and whether the
Receive Equalizer is enabled or not.
Table 5 presents the various voltage levels at the
LOSTHR input pin, the state of the Receive Equalizer
and the corresponding ALOS (Analog LOS) threshold
amplitudes.
Declaring ALOS
A channel(n) declares ALOS_(n) whenever the ampli-
tude of the receive line signal falls below the Signal
Level to Declare ALOS levels, as specified inTable 5.
Clearing ALOS_(n)
A channel(n) clears ALOS_(n) whenever the ampli-
tude of the receive line signal increases above the
Signal Level to Clear ALOS levels, as specified in
Table 5.
There is approximately a 2dB hysteresis in the re-
ceived signal level that exists between declaring and
F
IGURE
27. T
HE
B
EHAVIOR
OF
THE
LOS O
UTPUT
I
NDICATOR
IN
RESPONSE
TO
THE
L
OSS
OF
S
IGNAL
AND
THE
R
ES
-
TORATION
OF
S
IGNAL
Actual Occurrence
of LOS Condition
Line Signal
is Restored
Time Range for
LOS Declaration
Time Range for
LOS Clearance
G.775
Compliance
G.775
Compliance
0 UI
10 UI
0 UI
10 UI
255 UI
255 UI
RTIP/
RRing
RLOS Output Pin
T
ABLE
5: T
HE
ALOS (A
NALOG
LOS) D
ECLARE
AND
C
LEAR
T
HRESHOLDS
FOR
A
GIVEN
SETTING
OF
LOSTHR
AND
REQEN (DS3
AND
STS-1 A
PPLICATIONS
)
A
PPLICATION
REQEN S
ETTING
LOSTHR S
ETTING
S
IGNAL
L
EVEL
TO
D
ECLARE
ALOS
S
GNAL
L
EVEL
TO
C
LEAR
ALOS
DS3
1
1
<22mV
>90mV
0
1
<17mV
<70mV
STS-1
1
1
<25mV
>115mV
0
1
<20mV
<90mV
