TN: Open Source: Why is the Knox County Sheriff's office phone line going down? [telecom]

By Emma Davis, Report for America Corps Member

EDITOR'S NOTE: This story is in response to a reader-submitted question through Open Source, a platform where readers can submit questions to the staff.

MOUNT VERNON - Over the past few months, when community members have called the Knox County sheriff's office non-emergency line, the phone has rung, and rung, and has continued ringing without end.

This was because intermittent equipment malfunctions prevented the phone system from being triggered to take calls, said Kyle Webb, Director for Information Technology services in Knox County

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***** Moderator's Note *****

During the early days of the transition to Customer-provided equipment, many companies purchased PBX's from manufacturers that did not use "standard," Mother-Bell-Approved ringing voltages and grounding.

Except, once one of the PBX's wasn't made by Western by-Ghod Electric, things started to break. As a result, those PBX owners soon found themselves unable to use "Extensions Off Premise," which were PBX numbers that were connected to distant locations, such as the company's warehouse. Such lines, which worked fine when connected to the step-by-step electromechanical PBX's supplied by Western Electric, would sometimes not be able to relay ringing voltage supplied without a ground reference. For example, Rolm PBX's had something like 70 volts between tip and ring, usually enough to ring a "500" set, but it was floating, *NOT* referenced to ground, and would not, therefore, trip the "R" relay in some T-Carrier "FXO" (Foreign eXchange, Office end) channel units.

The solution, back then in the dark ages when dinosaurs roamed the earth, was that most of the PBX companies rushed to make their PBX's "compatible" with Western Electric equipment.

You're probably thinking, since this is 2021, "Why didn't they just dial '9' and make a regular call?" To which I, and probably many other old phone guys, would reply "Oh, you innocent children!"

In the bad 'ol days of Mother Bell's monopoly, prices (I almost wrote "rates," but few would understand) for even local calls between business locations were exorbitant, and most large companies went to great lengths to avoid any use of the PSTN that wasn't clearly unavoidable. Large companies would have "tie lines" in-between their PBX's, either from one operator position to another, or connected directly so that PBX users at either end could dial directly into the other PBX. The Tie Lines, which utilized DX signalling - the epitome of ground-referenced signalling, dating from early single-wire telegraph lines - would not work with the CPE PBX's that used isolated ground environments and didn't understand *ANY* ground-referenced lines.

The revisions, hardware modifications, and other work-arounds served for a few decades, but now that Western Electric is deader than the batteries that Thomas Alva Edison wanted to use to transport elec- tricity between cities, well, it seems some incompatibilities have crept back in to a no-longer-quite-so-well-integrated network.

Bill Horne Moderator

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