Specifications

AN93
120 Rev. 0.8
not only the functionality of the modem chipset after
assembly but also discrete parts and product-related
software. Therefore, finished product test requirements
and procedures depend on the manufacturer and the
product. Consequently, no universal final test procedure
can be defined.
Testing the modem in a finished product is done for
several reasons. First, it is important to be sure the
modem chipset and peripheral components were
installed correctly during assembly and were not
damaged. Second, it is necessary to be sure the correct
component values were installed and that there are no
manufacturing problems, such as solder bridges, cold
solder joints, or missing components.
Functional testing can be used to test special features,
such as intrusion detection, caller ID, and overcurrent
detection. An intrusion can be simulated by placing a
1kΩ resistor across TIP and RING through a relay.
Caller ID testing requires special test equipment, such
as the Rochelle 3500 or Advent AI-150.
Many manufacturers choose to use built-in self-test
features, such as the &T3 Loopback test described
above. Others do a complete functional test of the
modem by originating and answering a call and
successfully passing a data file in each direction. This
process tests the modem and line-side chip
functionality, the associated external components, and
the software controlling the modem. This test can be
done with a modem under test (MUT) and a known-
good reference modem or between two modems under
test. Testing two modems under test at once reduces
test and setup time. Modem operational testing is time
consuming and adds to product cost. It is up to the
manufacturer to determine whether operational testing
is warranted.
Analog modems (Bell 103 through V.34) can be tested
by connecting the modems through a telephone line
simulator, such as Teltone TLS-3. A call can be placed
or received in either direction at the speed set in the
modems. A test script must be written for a computer to
control the dialing, monitor the call progress, send a file,
and compare the received and sent file. Figure 24
illustrates this test configuration.
Figure 24. Bell 103–V.34 Modem Functional
Test Connection
V.90 modems must be tested with a digital modem,
such as the USR Courier I. If you do not use a digital
modem as illustrated in Figure 25, the highest connect
speed a V.90 modem will support is 33.6 kbps. A call
can be placed or received in either direction at the
speed set in the modems. A test script must be written
for a computer to control the dialing, monitor the call
progress, send a file, and compare the received and
sent file. Figure 25 illustrates this test configuration.
Figure 25. V.90 Modem Functional
Test Connection
Table 87 compares the coverage of &T2, &T3, and full
bi-directional functional testing.
Teltone TLS 3
Modem Under
Test
Reference Modem
Test
Computer
Test
Computer
Teltone
ILS 2000
ISDN Modem
Modem Under Test
ISDN
Terminal
Adaptor
ISDN
ISDN Analog