atcomsystems.ca/forum Forums Other TDM Phone Systems Vertical Telephones & Systems SBX line voltage

Ed, you're crazy. (You did ask for it.)

However, you are correct that manufacturers SHOULD make their stuff able to tolerate the full range of allowable voltages and currents. But many, many problems can be traced to high (or low) line current.

The problem is Ed there is no upper limit on loop current, just a minimum. I too have seen weird problems due to high loop current.

Actually, the FCC upper and lower limits are 23 ma and 120 ma.

Arthur, if you have any offical documentation that shows that I'd like to see it.

While I've seen the same limits you're stating I've never seen the ANSI, Telcordia, EIA, Bell System standards, or any other standard that actually stated it.

If you search on "loop current" on the forum this question has been asked many times.

Which should probably be addressed in a new topic or one of the loop current topics.

Thanks for all the info. The only standard I found was TIA 968-A which is referred to in the FCC part 68. If I'm reading it right the loop current should be between 23 - 120 ma. the dc voltage should not be more than 56.5. Now I know there are alot of standards out there but which one does Vertical/LG use to design these systems. I have asked them but still have not received an answer. I had one tech tell me something about ITU but that didn't come from an engineer. Unfortionately I could not find that standard free online. I would think that if it is a standard they are going to use then it should be available free or the manufacturer should be able to supply us with a copy. I will try the resisters when I get a chance. I did read that it should work.

JBW, where in that document did you find the values. I searched loop current in the document but didn't find those values. Could you give me the paragraph or page? Thanks.