David Wilson wrote:
On Aug 14, 4:04 am, "Michael J. Mahon" <mjma...@aol.com> wrote:And it would also be possible to use the yellow/black twisted pair for a NadaNet connection! ;-)I wouldn't recommend it... If someone shorts the two lines together will the NadaNet adapters withstand the 50VDC idle or ~100VAC ring voltages?
You make a good point, but I'd first recommend preventing people from shorting the two lines together! ;-) More seriously, that would require two different wiring faults to get pair 1 connected to pair 2. Either wire of either pair not being paralleled would greatly limit current flow (but would probably prevent NadaNet from working ;-). Each NadaNet adapter clamps the net to +5v in each Apple, and to ground through the emitter follower and its emitter resistance (which is admittedly a little high for a clamp at 4.7k). Adding a diode to hard clamp to ground (the opposite pair conductor) would be useful if a difficult environment is anticipated. Ultimately, I would use the "line 2" pair of a phone wire only if it was both difficult to run another wire and unlikely that someone besides me would be playing with the wire. -michael NadaNet file server for Apple II computers! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."