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15-4
C
15: T
HAPTER
ESTING THE CONNECTION
If you use the S18 test timer, but in the process of testing you issue a
ATZ command, S18 resets to zero and the timer is disabled. You cannot
store a value for S18 in NVRAM; its power-on and reset default is always
zero.
Using AT&T8
This analogue loopback option causes the Courier V.Everything modem
to send an internal test pattern to its transmitter and loop it back to the
receiver. An internal error detector counts any errors and, when the test is
ended, sends the number of errors or 000 (no errors) to the screen.
Since you don't type anything during this test, and the Courier
V.Everything modem does not send anything to the screen, this option
verifies only the Courier V.Everything modem. If there are no errors but
your problem continues, it may be at the computer interface.
1 Send
AT&M0&N3S14.0=0
This command disables error control, fixes the connection rate at 2400
bps, and makes the Couri e r V.Everything modem return to command
mode when you type
2 Send
to begin the test.
AT&T8
The Courier V.Everything modem enters analogue loopback (AL) mode,
and sends a CONNECT message. The MR status light flashes. The
V.Everything modem then sends its internal test pattern to the
transmitter, and loops the pattern back to the receiver. You will not see
any data on your screen.
3 Send the escape code,
Alternatively, you can end the test by sending ATH or ATZ. Be careful
because ATZ resets the modem in addition to ending the test
In any case, the Courier V.Everything modem hangs up and returns a
three-digit code, followed by OK.
The code
000
255
An ERROR message indicates that you issued an invalid command.
4 Send
, unless you used a reset command (ATZ or ATZ!).
AT&M4
to the modem prepare for testing.
.
+++
, and the
+++
AT&T0
Indicates
No errors were found
255 or more errors
to end the test.
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