On 5/26/06, Wouter van Ooijen wrote: > > So how > > best to provide protection when the polarity of the line will be > > changing? Let's guess that the line length will be between 50 and 400 > > feet of cat5 cable. > > A 3v9 zener diode + a small series resistor? So the zener would drop down my higher voltage to 3.9V, and the resistor would act as a current limiter, both on the remote end. That way I get to use a higher voltage on the sending unit side, correct? Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist