My question for TIA-968-A is: how can something be compliant with all the criteria in this standard "in spite of" been totally destructed? Does it mean it is ok if power adapter or power supply is dead or entire product, including voice port can be out?
Test Lab did the 2.5kV test, power adapter stopped producing DC, but no arcing, burning or enclosure breach. Lab concluded the failure.
Hi Mark:
The other responses you have received are all correct. For clarification, I would just add that the reason is that FCC Part 68 is a "harms-based" standard, as opposed to Telcordia GR-1089 and many other standards that are "performance-based." FCC Part 68 does not concern itself with whether your product works, or with how well it works. It only concerns itself with the ways in which your product can interfere with the proper functioning of the network.
Years ago, one of my colleagues liked to point out that "a block of wood will pass FCC Part 68." This is surprising but true, and I often quote this when trying to explain to clients that FCC Part 68 approval does not say much about the quality or usefulness of a product.
In the early days of FCC Part 68, the "harms-based" philosophy was pretty clear. Functional failure as a result of the lightning test was fine as long as the equipment became essentially an open circuit presented to the phone line. In subsequent years the requirement to survive the "Type B" surge was added based on the argument that failures could "harm" the network by causing unnecessary service calls to the service providers from customers complaining that their phone service had stopped. This change was controversial at the time because it stretched the definition of a network "harm." Failure in response to the more severe "Type A" surge remains allowable.
Another functional requirement that appears in FCC Part 68 is for hearing aid compatibility for equipment that has a handset, but that is a result of Federal legislation, not the harms-based philosophy behind the standard.
Note that even though the Type B surge and the hearing aid compatibility performance requirements appear in an otherwise purely harms-based FCC Part 68, the previously mentioned block of wood will pass both of those tests.
By the way, I agree with a previous response that the FCC Part 68 2500 volt surge is fairly modest. If your power supply is really being damaged by this surge, you will likely have a high level of field failures with this product, even if you do manage to persuade the test lab that the product passes FCC Part 68. You would be well advised to look into the failure mode and make changes to improve the performance. For good field reliability, I recommend a self-imposed requirement of 5000 volts for common mode (longitudinal) surges on tip/ring.
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
http://www.randolph-telecom.com -
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