At 04:57 PM 9/16/2003 -0300, Mauricio Jancic wrote:

>Can you please explain to me what is the difference between a "wet" and
>a "dry" interface?

in a dry interface, the loop current does not go through the transformer.  this is nice, because your transformer in a wet interface, needs to have high resistance, as well as not saturate with as much as 100ma flowing through it.  transformers for wet interfaces are typically rather large, say 2x-5x in volume, relative to a dry interface transformer.

in a dry interface, the transformer is ac coupled to the line, and loop current is usually passed through a two transistor constant current circuit, though i've seen resistive methods used, which makes impedance matching more difficult.  constant current circuits have nearly infinite impedance.

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