Phone line hum

[haertig]

Just like OTA antennas, phone lines can NOT be split indefinitely...

What is a phone line "splitter"? This can't be some lossy thing like your basic RF splitter with a small transformer inside. All your tips and rings are just hooked up in parallel. There's really no loss involved in the "split", other than the tirival loss inherant to any direct electrical connection. Of course all the impedances of the phones plugged in will add up and load down the line, but I haven't seen that present much of a problem for several years. Back when phones had those bell ringers you had to be aware of your total connected REN ("Ringer Equivalence Number"). I have seen cases recently where one cheap device hooked up to the phone line messes up other things connected. My daughter received an el-cheapo phone for a gift a while back and it caused problems. It wasn't the split wiring's fault, rather the piece of junk plugged in to one of the outlets.

 

[SimpleSimon]

For voice transmission, the slight amount of noise/capacitance/induction and all that junk that are picked up don't matter at all.

However, when it comes to 56K modems, it's a different story entirely because they are pushing the corners of the envelope. Remember that 56K is actually limited to 52K (or is it 53?) by the FCC because getting there requires more power than the lines can actually handle.

Sometimes it matters, sometimes it doesn't. These guys are having the problem - so maybe it matters for them.