Select the second channel to be used for Modem 4em or Modem 8em
loopback testing.  The first of the two channels was selected by
pressing the T (or t) key from the channel monitoring screen.
Press the ESC key to cancel loopback second channel selection or to
select a different first channel.

Select the second loopback channel by pressing a number from the list
of valid channel numbers shown on the screen.

The Print Screen (^P) option invokes a screen dump  to  the  default  file
/tmp/dpalog.   If  another  file and/or path is desired, simply invoke dpa
with the -l option.
        e.g.       dpa -l <logfile>
