XRT86L30
REV. 1.0.1
SINGLE T1/E1/J1 FRAMER/LIU COMBO
Receive Interface with 1:1 and 1+1 Redundancy
4.2.5
The receivers on the backup card should be programmed for "High" impedance. Since there is no external
resistor in the circuit, the receivers on the backup card will not load down the line interface. This key design
feature eliminates the need for relays and provides one bill of materials for all interface modes of operation.
Select the impedance for the desired mode of operation, T1/E1/J1. To swap the primary card, set the backup
card to internal impedance, then the primary card to "High" impedance. See Figure 10. for a simplified block
diagram of the receive section for a 1:1 redundancy scheme.
F
IGURE 10. SIMPLIFIED BLOCK DIAGRAM OF THE RECEIVE INTERFACE FOR 1:1 AND 1+1 REDUNDANCY
Backplane Interface
Primary Card
XRT86L30
1:1
T1/E1 Line
Rx
Internal Impedence
Backup Card
XRT86L30
1:1
Rx
"High" Impedence
146
EXAR [ EXAR CORPORATION ]
