"according to TWC tech support they are transmitting at "48 decibels"

Such a statement is indicative of a 'technician' who doesn't have a clue what they are talking about. This technician needs to understand that trunk voltage and transmit levels are completely different issues. This genius also needs to connect a voltmeter to the trunk ports at your premises and show you that the voltage is beween 48 and 52 volts DC when on-hook. If they can't prove this, then you win the battle.

Oh, and as for the matter of the fax line: Fax machines are much more tolerant to line voltage inconsistencies. PBXs are designed to work with precise line (trunk) voltages. This is a standard that has existed for many, many decades.

If each trunk cannot provide ~48 volts DC between tip and ring and between ring and ground, then you do not have true PBX trunks or even POTS lines for that matter. Please copy/paste this paragraph and show it to TWC.

You need to seriously think about this: Is TWC really saving you any money? They have already proven that they don't know what they are doing. Your SX50 was working fine until they entered the picture. Now all of a sudden your system is causing the problem? Yeah, OK..........

Come on, stop and look at the big picture. I'd go back to Verizon and find other places to save money. CLECs don't follow FCC standards (despite the fact that they are supposed to). They offer cheaper rates by tossing their customers under the bus when something goes wrong.

Ed Vaughn, MBSWWYPBX