INTERNATIONAL  TELECOMMUNICATION  UNION

		     ITU-T RECOMMENDATION SUMMARY


Rec. No. : K.20

Title :	Resistibility of telecommunication switching equipment to 
	overvoltages and overcurrents

Study Group : V - Protection against Electromagnetic Effects

Version : Revised

Date of adoption : 1991

Notes :	


Recommendation K.20 seeks to establish fundamental testing methods and 
criteria for the resistibility of telecommunication switching 
equipment to overvoltages and overcurrents. It should be read in 
conjunction with the CCITT Manual, Protection of telecommunication 
lines and equipment against lightning discharges and 
Recommendation K.11 which deals with the general economic and 
technical aspects of protection. The methods may be varied in the 
light of particular local circumstances and technical developments.

Recommendation K.20 relates to telephone exchanges and similar 
telecommunication switching centres and is concerned mainly with test 
conditions to be applied to points intended for the connection of 
2-wire subscriber lines. Ports carrying more complex circuits or more 
concentrated traffic (such as junctions or multi-channel circuits) may 
be tested either in accordance with Recommendation K.20 or in 
accordance with other Recommendations such as K.15 and K.17, as 
considered appropriate.

The tests are type tests and, although they are applicable to a 
complete switching centre, it is recognized that they may be applied 
to individual items of equipment during development and design work. 
In making the tests, it is necessary to take account of any switching 
conditions, either in the unit under test or elsewhere, which may 
affect the results.



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