Download TIA-968-A leakage question - Telecommunications Industry

TR41.9-07-11-005
Title: TIA-968-A leakage current question
Distribution to: TIA TR41.9
Meeting Location: Albuquerque, NM
Novemeber, 2007
Submitting Littelfuse
Organization:
Contact Phillip Havens
Information: Littelfuse
1800 Hurd Drive
Irving, TX 75038
Phone (972) 518-9427
Fax (972) 550-1309
Email : [email protected]
Keywords: TIA-968-A
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TR41.9-07-11-005
TIA-968-A contains the following paragraphs:
Note 4 to table 4.1
A telephone connection, auxiliary lead, or E&M lead that has an intentional dc
conducting path to earth ground for protection purposes at the leakage current test
voltages (such as through a surge suppressor), may have the component providing
the conducting path removed from the equipment for the leakage current test in that
operational state. Components removed for this reason shall comply with the
requirements of section 4.4.5.2.
4.4.5.2 Connections with protection paths to ground.
Approved terminal equipment and protective circuitry having an intentional dc
conducting path to earth ground for protection purposes at the leakage current test
voltage that was removed during the leakage current test of section 4.3 shall, upon its
replacement, have a 50 or 60 Hz voltage source applied between the following points:
a)
Simplexed telephone connections, including tip and ring, tip-1 and ring-1,
E&M leads and auxiliary leads, and;
b)
Earth grounding connections.
The voltage shall be gradually increased from zero to 120 V rms for approved
terminal equipment, or 300 V rms for protective circuitry, then maintained for one
minute. The current between (a) and (b) shall not exceed 10 mAP at any time. As an
alternative to carrying out this test on the complete equipment or device, the test
may be carried out separately on components, subassemblies, and simulated circuits,
outside the unit, provided that the test results would be representative of the results
of testing the complete unit.
1) Why is the voltage level restricted to 120 V rms for approved terminal
equipment but then increased to 300V rms for protective circuitry? What
are the technical details that push for these two different voltage levels?
2) What is the definition of “protective circuitry”?
3) How does one distinguish between approved terminal equipment and
protective circuitry? (Isn’t protective circuitry found in terminal
equipment?)