Telenetics DSP9612RM - Manual (Page 28)

Installation
Page 28
Loopback Control Switch
The front panel of the modem has a push button for initiating the
following loopback diagnostic tests:
c Local analog loopback  started by pressing the button one time.
c Local digital loopback  started by pressing the button two times.
c Remote digital loopback  set the local modem’s RTS signal to
low. Then press the remote modem’s diagnostics button three times
and raise the local modem’s RTS signal to start the test. The ALB
and DLB LEDs go ON when the modem is in remote digital
loopback. This test is only available in Fast Poll mode only.
Figure 2-6 illustrates these three diagnostics.
Figure 2-6. Loopback Diagnostics