XRT83SH38ES View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT83SH38ES' PDF : 78 Pages View PDF
XRT83SH38
REV. 1.0.7
8-CHANNEL T1/E1/J1 SHORT-HAUL LINE INTERFACE UNIT
5.2.4 N+1 Redundancy Using External Relays
N+1 redundancy has one backup card for N primary cards. Due to impedance mismatch and signal
contention, external relays are necessary when using this redundancy scheme. The relays create complete
isolation between the primary cards and the backup card. This allows all transmitters and receivers on the
primary cards to be configured in internal impedance, providing one bill of materials for all interface modes of
operation. The transmit and receive sections of the LIU device are described separately.
5.2.5 Transmit Interface with N+1 Redundancy
For N+1 redundancy, the transmitters on all cards should be programmed for internal impedance. The
transmitters on the backup card do not have to be tri-stated. To swap the primary card, close the desired
relays, and tri-state the transmitters on the failed primary card. A 0.68uF capacitor is used in series with TTIP
for blocking DC bias. See Figure 29 for a simplified block diagram of the transmit section for an N+1
redundancy scheme.
FIGURE 29. SIMPLIFIED BLOCK DIAGRAM OF THE TRANSMIT INTERFACE FOR N+1 REDUNDANCY
Backplane Interface
Primary Card
XRT83SH38
Tx
0.68uF
Internal
Impedence
Primary Card
XRT83SH38
Tx
0.68uF
Internal
Impedence
Primary Card
XRT83SH38
Tx
0.68uF
Internal
Impedence
Backup Card
XRT83SH38
Tx
0.68uF
Internal
Impedence
Line Interface Card
1:2
1:2
1:2
T1/E1 Line
T1/E1 Line
T1/E1 Line
38
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