Moshe Hello!

Let me re-phrase your question. You are asking is a transient 
voltage suppressor can bridge "basic insulation" between a TNV-3 
circuit as defined in UL1950/EN60950 and an unearthed chassis? 

Personally, I believe this is OK for North America (if you are using 
a Recognized suppressor suitable for the ratings). However, this 
could cause problems for Europe where spark gaps are preferred.

Before you implement the design of your telephone interface, I 
suggest you consult with the appropriate Third Party Safety/EMC 
Telecoms Certification Agencies who will eventually test and 
Approve your equipment.





> Hello everyone,
> 
> In a telecommunication device I need to connect a transient suppressor from 
> the phone line 
> to the metal chassis, which is not safety grounded. (I believe this is 
> defined a class II 
> device).
> Are there any special considerations / limitations in this condition?
> 
> thanks in advance,
> moshe
> 
>d
> 


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