JUNE 1998 - REVISED JULY 2008

Specifications are subject to change without notice.

Customers should verify actual device performance in their specific applications.

Indoor POTS Lines to ITU-T Recommendation K.21. K.22 and IEC 61000-4-5: 1995

TISP6NTP2A Programmable Protector

Internal POTS lines from WILL and ISDN-TA equipment are in a relatively unexposed environment. If these lines are galvanically isolated

(floating), the return path for any induced surges can only be through equipment capacitance or insulation breakdown.

The most stressful condition would be when the POTS lines are not galvanically isolated. Such a case is when an ISDN-TA has a common

connection between the incoming ISDN line and the internal POTS lines. The ISDN line is likely to be ground referenced and may have primary

protection at the subscriber connection. If the primary protection operates, it provides a direct return to ground.

ITU-T recommendation K.22 for a floating 4-conductor T/S bus uses a 1 kV 1.2/50 or 2/10 impulse, capacitively coupled via 8 nF to the bus

conductors. Very little circulating current is likely to flow during K.22 testing. If the T/S bus has a ground return, then the testing changes to

ITU-T recommendation K.21. The required series resistor values for K.21 and the TISP6NTP2A have been calculated earlier.

In IEC 61000-4-5: 1995 the highest specified test level is class 5. For unshielded symmetrically operated lines, class 5 testing uses a 4000 V

combination wave (1.2/50, 8/20) generator to apply a simultaneous impulse to all conductors. For the four conductors of the two POTS lines,

the currents are equalized by the use of specified 160 Ω feed resistors. As the generator fictive source impedance is 2 Ω, the peak current in

each conductor is 4000/(2x4 + 160) = 24 A. This is less than the 60 A TISP6NTP2A rating.

If the lines are long and exit the building, testing is done with a 10/700 generator. In this case the feed resistors are 100 Ω and the fictive

impedance is 15 Ω. The peak current in each conductor will be 4000/(15x4 + 100) = 25 A. This value is the same as the TISP6NTP2A rating.

As the equipment connected to the POTS line may have uncoordinated protection, it is desirable to provided the ring-tip pair current sharing to

the TISP6NTP2A by series resistors (R1A, R1B, R2A and R2B). A value of 4 Ω should be sufficient to ensure sharing.

APPLICATIONS INFORMATION

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