Multitech MMH900, User Manual

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Appendix I - Testing Your MMH 2834
I.2 Local Analog Loopback Test/V.54 Loop 3
In this test, data from your computer or terminal is sent to your modem's
transmitter, converted into analog form, looped back to the receiver,
converted into digital form and then received back at your monitor for
verification. No connection to the phone line is required. See Figure I-1.
UUUUU
UUUUU
Local MultiModem
Computer or Terminal Computer or Terminal
Type ATU0 or ATU1; hit ENTER
Digital Analog
Figure I-1. Local Analog Loopback Test
The test procedure is as follows:
1. Connect the modem to your computer. With your communication
software, set the desired baud rate.
2. Type ATU0 (or ATU) and hit ENTER. This places your modem in
Analog Loopback mode, in the Originate mode. The modem is now
out of the Command mode and in a pseudo On-Line mode.
3. Once you receive a connect message (if responses are enabled),
enter data from your keyboard. For this test, typing multiple upper
case "U" characters is a good way to send an alternating test pattern
of ones and zeros.
4. For a more complete test, you should also test the modem in Answer
mode. To do this, you must “escape” from Originate mode by
entering an Escape Sequence (+++AT<CR> or <BREAK>AT<CR>)
. Then type ATU1 and hit ENTER to place the modem in Analog
Loopback mode, in the Answer mode. Then repeat step 3.
5. When testing is completed, you may exit Answer mode by entering
an Escape Sequence (+++AT<CR> or <BREAK>AT<CR>), which
returns the modem to Command mode.
6. Your modem passes this test if the data entered from your keyboard
are the same as the data received on your monitor. If different data
is appearing on your monitor, your modem is probably causing the
problem, although it could also be your computer. If your modem
passes this test, but you are receiving errors while On-line, the
remote modem or the phone line could be at fault.