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MT202TD User Guide
18
Chapter 3 - Modem Testing
Introduction
The MT202TD has two diagnostic tests: Local analog loopback
and digital loopback.
A loopback test involves entering data from your PC and
looping that data through the circuits of your modem and/or a
remote modem. When the loop has been completed, the data
received on the monitor should match the data entered on the
keyboard.
The local analog loopback test allows you to verify that the
modem’s transmit and receive circuits are functioning properly.
Refer to the
Local Analog Loopback
section on the following
page for more details.
The digital loopback test allows you to verify that the local
computer or terminal, the two modems, and the transmission
line between the devices are functioning properly. See the
Digital Loopback Test
section in this chapter for more
information.
Local Analog Loopback Test
The analog loopback test is performed by placing the analog
loopback (ALB) switch in the ALB position (see Figure 2-3 in
Chapter 2 of this user guide). When the switch is set to the ALB
position, the CD, CTS, RTS, DSR, and TM indicators should
light.
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. The TD and RD indicators blink as keys
are pressed. If your modem is configured for two-wire opera-
tion, the Local Copy DIP switch must be enabled (see Chapter