Black Box MD1640A, MD1641A manual 119

CHAPTER 8: Modem Testing

In this test the local modem is placed in Digital Loopback mode. Data is entered and transmitted from the remote modem (which is not in digital loopback mode), sent across the phone line to the local modem and looped back to the remote modem.

The test procedure is as follows:

1.Go into Terminal mode. Type AT and hit ENTER; you should get an OK message.

2.Dial the remote modem by entering the Dial command and the phone number, to establish On-line mode.

3.Type the Escape Sequence (+++AT<CR> or <BREAK>AT<CR>) which brings your modem into Command mode, while still main- taining the pseudo On-line mode with the remote modem.

4.Type ATU3 from the local PC and hit ENTER. Once you receive an OK message from your modem (if responses are enabled), the local modem is placed in Digital Loopback mode.

5.Data is typed from the remote keyboard. For this test, typing multiple upper case "U" characters is a good way to send an alter- nating test pattern of ones and zeros. The data received by the local modem will enter its analog receiver, be converted to digital data, be reconverted into analog, and then looped through its transmitter back to the remote modem. Your modem passes this test if the data entered from the remote keyboard is the same as the data received on the remote monitor.

6.When testing is complete, you may end the test by typing an Escape Sequence (+++AT<CR> or <BREAK>AT<CR>) to bring your modem into Command mode. The modem should respond with an OK message. If you wish to stay On-line with the remote modem for normal data transmission, type AT0 and hit ENTER. If you wish to terminate the call, type ATH and hit ENTER to hang up.

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