C Loopback Tests
Test Procedure
1.Open your communications software and go into terminal mode. Type AT and press ENTER; you should get an OK message. Type AT\N and press ENTER to disable error correction. Type AT+MS=9,1,9600,9600 and press Enter to set the local modem to V.32 mode at 9600 bps.
2.Dial the remote modem and establish your online connection.
3.Type the escape sequence +++AT and press ENTER to bring your modem into online command mode.
4.Type AT&T3 and press ENTER. Once you receive an OK message from your modem (if responses are enabled), your modem is placed in digital loopback mode.
5.Have someone enter data from the remote keyboard. For this test, typing multiple uppercase U characters is a good way to send an alternating test pattern of binary ones and zeros. The data received by your modem enters its analog receiver, is converted to digital data, is reconverted into analog, and then is transmitted back to the remote modem. Your modem passes this test if the data received on the remote monitor is the same as the data entered from the remote keyboard.
6.To exit the test, turn off the modem.
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