In principle, you will want to test the system with modem in its various "operating modes." For emissions testing, this would typically mean the "on-hook" idle state and the off-hook data mode where the modem has an active data connection with another modem. For immunity testing (at least under the EN 55024 test I am familiar with), you are also supposed to test the modem's ability to establish and then take down a data call.
All of the required test modes are accessible through set of special test commands in the Multitech modem. So, aside from using the test modes to put the Multitech modem in the desired operating state, you will need a second modem to serve as the auxiliary equipment, an appropriate LISN, and a way to simulate the operation of a telephone central office. Companies such as Teltone make simple CO simulators.
Note that what I have described is a "by the book" interpretation of how the tests should be applied. Some test labs take short cuts, such as simply testing the modem in the on-hook and off-hook states, without actually setting up data calls.
If you have further questions about how to do these tests, feel free to contact me off-line.
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
[email protected]
http://www.randolph-telecom.com
I have a product where we added a Multitech modem module as per their examples and ran it through UL/CUL safety evaluation already.-
I am looking for some advice on a clean way to do EMC testing on this POTS Modem interface.
Both emissions (looking for FCC class B) and immunity to IEC61326
I have never evaluated a modem before.
I assume there is a way to simulate a POTS interface and isolate my aux monitoring equipment .
Any feedback would be appreciated.
Chris Wells
Eaton
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