Black Box MD1641A Manuale Utente
117
CHAPTER 8: Modem Testing
8.2 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 8-1.
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 8-1.
Figure 8-1. 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.
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.
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.
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 (
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.
Then repeat step 3.
UUUUU
UUUUU
UUUUU
Type ATU0 or ATU1; hit ENTER
Computer or Terminal
Local Series II Modem
digital
analog