User`s manual

&T7 Initiates RL/TP -Remote Loopback with a DSU/CSU generated 511 test pattern. At the end of the
test an error count is returned to the DTE followed by a valid command response. Anything other than an error count of 000
indicates data errors were received
&T8 Initiates LL/TP - Local Loop with a DSU/CSU generated 511 test pattern.At the end of the test
an error count is returned to the DTE followed by a valid command response. Anything other than an error count of 000
indicates data errors were received.
&T9 Initiates TP - An internally generated 511 test pattern is transmitted.
At the end of the test an error count is returned to the DTE followed by a valid command
response. Anything other than an error count of 000 indicates data errors were received. (Max count is 255.)
&X timing control
This command configures the source of the TXCLK (powerup configuration is defined by DIP switch 3).
&X or &X0 Selects the DSU’s internal timing source.
&X2 Slave timing - Receive clock is the timing source.