Telenetics MIU PowerPort 2.4, Installation & Operation Manual

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MIU Installation, Operation & Diagnostics Edition: January 25, 1999 Page 22
This is a system test, end to end.
The command is valid only if the modems are in the command state with a
connection established.
Configure the remote modem with an AT&T4 command so that it will
honor a remote digital loopback request.
Enter AT&T7 at the local modem and it will send a digital loopback
request to the remote modem. After the RDL acknowledgment signal is
received from the remote modem, DSR is turned off (if &S1 is in effect),
the on-line state is entered, an OK result code is sent to the DTE, and the
test timer is set to the value in S18. While the test is active, the local
modem sends a test message to the remote modem and counts the errors in
the received (looped back) signal. The modems stay in the command
state during the test. When the test is terminated (except by a loss of
carrier), the local modem sends the release signal to the remote modem, as
in &T6, and reports the three-digit error count to the DTE.
The information text is followed by an OK result code. The test is
terminated by loss of carrier, or an H0, &T0, or Z command, and by the
S18 timer running out.
RESULT CODES
DESCRIPTION
OK When command executed is started.
OK After error count is sent to DTE (&T1,
&T3, &T6, &T7 or &T8).
ERROR If not in on-line command state.
ERROR If the RDL signal is not acknowledged.