Chapter 5 - Testing the Modem
2.Dial the remote modem by entering the Dial command and the phone number, to establish
3.Type the Escape Sequence (+++AT<CR> or <BREAK>AT<CR>) which brings your modem into Command mode, while still maintaining the pseudo
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 alternating 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.
Computer or Terminal | Computer or Terminal |
| UUUU |
Local Modem | Remote Modem |
Digital Analog Analog
Digital
Figure 5-2. Digital Loopback Test (local / manual)
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
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