Northern UTA220/UTA220k - Manual (Page 125)

UTA220/UTA220k
14-5
Diagnostics
Bilateral Loopback Test
Bilateral loopback combines the functions of local loopback
and digital loopback. Its loops data from the local terminal
back to the terminal, so that whatever the terminal sends is
echoed back (Figure 14-5). Also, it loops to where the ISDN
B-Channel data normally sent to the local DTE. Any
B-Channel data received by the UTA220 is processed by the
rate-adaptation protocol, and then echoed back out the
B-channel to the sending unit. This test is useful in diagnosing
the DTE, UTA220, switch, ISDN line, and remote unit. Run
this test if you are encountering data errors after a call is placed
successfully.
Figure 14-5. Bilateral Loopback Test