Verilink Productivity 500 (34-00236) Product Manual - Manual (Page 77)

Test Mode Operation 500 TA Page 77
rate may be used although the protocol on the two units must be compatible.
The remote unit should be set to the same rate adaptation protocol as the local
500 TA, and left in normal data mode. Data sent by the remote TA will be
received by the local 500 TA, then echoed back to the remote TA. The test is
successful if the data is correctly echoed back to the sender. A BERT device
can be helpful in checking for data errors.
Figure 8 Digital Loopback
The test should be run in both directions if possible (i.e. use the local 500 TA as
both the sending unit and as the loopback unit). If the B-channel data test is
successful, it indicates that the local and remote units and network are func-
tioning. If there are errors, the problem could be in any of those elements.
The test is terminated by entering AT&T0.
Bilateral Loopback Test &T8
Bilateral loopback combines the functions of local loopback and digital loop-
back. Its loops data from the local PC back to the PC, so that whatever the PC
sends is echoed back (
Figure 9 ). Also, it loops the ISDN B-Channel data nor-
mally sent to the local PC. Any B-Channel data received by the 500 TA is pro-
cessed by the rate-adaptation protocol, and then echoed back out the B-channel
to the sending unit. This test is useful in diagnosing the PC, 500 TA, switch,
ISDN line, and remote unit. Run this test if you are encountering data errors
ISDN
Interface
DTE
Interface
ISDN
Line
ISDN
Receiver
ISDN
Transmitter
Protocol
DTE
ISDN
Interface
DTE
Interface
ISDN
Line
ISDN
Transmitter
ISDN
Receiver
Protocol
Remote Unit
Local Unit