from
The Collaborative International Dictionary of English v.0.48
barretter \bar"ret*ter\, n. [OF. bareter to exchange. Cf.
{Barter}.]
1. (Electronics) a resistor inserted into a circuit to
compensate for changes (such as those arising from
temperature fluctuations); a thermal cymoscope.
Syn: ballast resistor.
[Webster 1913 Suppl. + WordNet 1.5]
Note: The original form consisted of an extremely fine
platinum wire loop attached to terminals and inclosed
in a small glass or silver bulb. It operates by
increased resistance when subjected to the influence of
an electric current. In a later variety, called the
{liquid barretter}, wire is replace by a column of liquid in
a very fine capillary tube. A recent version has a
resistor composed of an iron wire in a glass bulb
containing hydrogen, with the temperature variation of
resistance such that the current passing through it
remains constant over a wide range of applied voltages.
[Webster 1913 Suppl. + PJC]