There have been endless argument about what is and is not a telecom*****. It will never be settled to everyone's satisfaction. however, responding to just a little of what you said,
> I would contend that TNV lines can only be those lines which are > conductively connected to public telecommunications lines/and or which can > generate telephone ringing voltages. We are trying to come up with safety criteria here. The ownership of a line is not usually important with regard to safety and in some respects ringing voltages are not the issue. The major concerns are shock and fire risk from voltages and currents on the line, and the consequences of equipment faults, lightning and power cross. The standards are trying to address the risks and have had a lot of trouble integrating such factors as contact area, voltage, source impedance, period, load sensing, legacy products, international variations, and so on, but we try, and we have been tearing our hair out on definitions. One major distinguishing feature is what telecom people have called outside plant. The exposure to lightning and power cross are critical concerns. Anyone intending to run a line to a roof or outside buildings needs to give careful consideration to what has been written for TNV1 and TNV-3 circuits regardless of what they are called, be they RS232, or just a long piece of wire. Calling a piece of wire SELV may make design rules easy and may be within the definitions, but it may be unwise if you are ignoring the risks. Bob --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
