Black Box MD1641A, MD1640A manual Digital Loopback Test Local/Manual Synchronous Mode

SERIES II INTELLIGENT DATA/FAX MODEMS

To initiate the Local Analog Loopback Test, with the modem in Synchronous mode:

1.Enter AT&M1U. This first switches your modem form asynchro- nous to synchronous mode, and places it into the Analog Loop- back/Originate mode. The modem is now out of the Command mode and in the pseudo On-Line mode.

2.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.

3.For a more complete test, you should also test the modem in Answer mode. To do this, Type the Escape Sequence (+++AT<CR>

or <BREAK>AT<CR>) which brings your modem into Command mode, while still maintaining the connection. Then type AT&M1U1 and hit ENTER to place the modem in Analog Loopback mode, in the Answer mode. Then repeat step 2.

Computer or

Terminal

UUUUU UUUUU

Local Series II Modem

digital analog

Type ATU0 or ATU1; hit ENTER

Figure 8-5. Synchronous Mode Local Analog Loopback Test

8.8Digital Loopback Test (Local/Manual) (Synchronous Mode)

This test must be run when you have a data connection with another modem. If a Local Analog Loopback Test resulted in errors, and this test passes without errors, then the problem exists in your computer-to- modem connection. In Digital Loopback Test (local/manual) mode,

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