Hi all,

A device for limiting currents,  used many years ago was called a "baretter". I came accross them old er universal AC/DC radios but also I saw them used in terminal units (TU's) of teleprinters..  They tended to have very low resistance when cold or warm, but the resistance went up very quickly to many times it's normal resistance when it got to the point where it would glow very brightly.  I think they were made by Osram.

I used to use them in faulty finding of "crossbar" telephone exchanges.  If I fuse was continuously blowing it was temporarily replaced by a baretter and when the fault occurred, it would limit the current to a safe value to avoid fires and allow identification of what relays were operated  in the relay set.

I do not know where you would getthem these days, you could try Googling.

Lee de Vries VK3PK
 

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