&T3 - Perform Local Digital Loopback

Command Line Format
AT [cmds] &T3 [cmds] <CR>

Suffix Values
N/A

Default
N/A

Stored by &Wn
N/A

Displayed by &V
N/A

Description
The modem must be in the Online Command State when this command is issued. Otherwise an ERROR result code occurs.

This command establishes a loopback of received data, after demodulation, and returns it to the distant end. The modem is configured for local digital loopback, DSR is turned off (if &S1 is in effect), the test timer is started with the value in S18, and an OK result code is sent to the DTE.

If S18 contains a 0, the test must be terminated by a &T0, H0, or Zn command. The latter two result in the modem going on hook. If S18 does not contain 0, the test is terminated after the number of seconds stored in S18.

The MR light flashes while the test is in progress.

Result Codes
OK - after 2 s delay

ERROR - if any other self test is active (&T1, &T6-&T8) or if in Idle State.

OK - when test is terminated.

Execution Time
Determined by test timer or until aborted by a command.

DTE Interface Lines Affected
DSR

LEDs Affected
MR flashes

Cross Reference
Commands - &Sn, &T0, Hn - Control The Switchhook , Zn - Perform Soft Reset
S-registers - S18
DTE signals - DSR

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