Telephones Analog & Digital Explained

In this video I discuss the theory and testing of both analog and digital telephones. Beginning with analog POTS (Plain Old Telephone Service) operation in making and receiving calls. Then finishing with digital telephone operation and demonstration using WireShark.

[@joshe9518]

You seem knowledgeable on this. Would you have any idea as to why only some of the buttons on a phone generate a tone ? I have 50vDC, new jack, new phone but I only have the bottom rows of tones from button presses… my thought is bad wire getting induced voltage from nearby 480 VAC motor circuits but I do not know. Any tips would be appreciated.

[@dc95811]

I would want to do a double swap with a known good phone. Does the "bad" phone still not work when plugged in to a jack that usually works? And does the phone that is known to work show the same "bottom row only" effect when plugged into the original jack? My guess from those symptoms is that it's just a bad phone.