Dear OMs,
At Helmut Singer Elektronik (http://www.helmut-singer.de ) I have bought an     

Radio Accessories
Funkzubehör
MIL
Clansman HEADSET TYP II, 

with useful noise cancelling. I just had to build an ps 12V/ 24 V with an 
dcdc-converter and hade to change some plugs. It is rugged, but dirty, nearly 
trash and I had to return the first parcel.  But  it is effective, as it is an 
closed system, like ear protectors in noisy environment.  No telephone bell, 
doorbell will penetrate through. 
Just try.
55,
Hans-Albrecht
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