Dear Listmembers,
I'm having a product tested to UL 1950/CSA 950 for the US and Canadian
market. This product is central office equipment powered by -48 vdc.
It sources -48 vdc to outside plant leads. The -48 is referenced to
ground, as needed for proper operation of signalling.
The test lab claims I need separation between TNV-3 and other parts of the
equipment, according to clause 6.4.1 dated March 1, 1998.
Clause 6.4.1 says separation from TNV-3 must be provided to:
a.. unearthed conductive parts...etc., not applicable to our equipment.
b. parts that can be touched ...etc., not applicable
c. circuitry which is provided for connection of other equipment and
telecommunication circuitry (other than earth) intentionally isolated
from telecommunication conductors.... My equipment is not
intentionally isolated, it is ground referenced.
The test lab decides to perform fault testing. This involves
injecting a ring signal from the outside through the tip/ring leads
and measuring the current through a 500 Ohm resistor. It fails to no
surprise, because there is an intemtional path to ground. Their claim
is, even though my equipment passes the overvoltage/power cross tests,
it could retransmit the external fault.
Am I missing something here? Or do I need to find another lab?
Regards,
Eric Petitpierre
Pulsecom
Herndon, VA
[email protected]
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