Verilink 2000 (34-00182) Product Manual - Manual (Page 46)

4-12 T ERMINAL O PERATION
T1 Loop
This field is used to select the test loops to be initiated. The type of loop is chosen
by toggling the spacebar and is executed by pressing Enter. The near-end loops
require that a Keep Alive signal be selected. There are five available loopback
options. The following paragraphs and diagrams give detailed descriptions. The
symbol represents an ignored signal.
NET LLB. The NET LLB loop returns network RXD to TXD with signal
regeneration only. Toward the DTE side, the CSU may be optioned to send AIS on
DTE TXD or LOOP back DTE RXD to TXD as shown in Figure 4-9.
DTE LLB. The DTE LLB loop (Figure 4-10) returns DTE RXD to TXD with
signal regeneration only. Toward the network side, the CSU may be optioned to
send AIS on network TXD or LOOP back network RXD to TXD.
FAR PLB. Executes a network payload loopback at the far-end CSU. The unit in
loop sends AIS to the DTE.
FAR LLB. Executes a network line loopback at the far-end CSU. The unit in loop
sends AIS to the DTE.
Framing, CRC, FDL
Tx
Rx
Rx
Tx
NET LLB, AIS to DTE
DTE
Interface
AIS
NET
Interface
Framing, CRC, FDL
Tx
Rx
Rx
Tx
NET LLB, LLB on DTE
DTE
Interface
NET
Interface
Figure 4-9 Network Line Loopbacks
Framing, CRC, FDL
Tx
Rx
Rx
Tx
DTE LLB, AIS to NET
DTE
Interface
NET
Interface
AIS
Framing, CRC, FDL
Tx
Rx
Rx
Tx
DTE LLB, PLB on NET
DTE
Interface
NET
Interface
Figure 4-10 DTE Line Loopback