Keep in mind that FiOS dial tone is not real, as in not to the same specs as traditional copper. In most instances, it is due to the lower line voltage that the FiOS ONT provides. Real lines are supposed to deliver somewhere in the neighborhood of 48 volts, where fake dial tone gadgets often deliver voltages that are much lower.

KSU-less phone 'systems' rely upon precise variances in voltage due to line condition in order to operate. For example, when going off-hook on a traditional line, the 48 volts drops down to somewhere below 10 volts. These phones are designed to monitor these changes in voltage to signal what is happening to the other phones on the line. With fake dial tone, these voltage relationships are pretty much tossed out the window.

Granted, these phones are old, but they're doing exactly what they are supposed to do. They're just being given bad information to work with when the line voltages are out of spec. Unfortunately, Verizon, Vonage, MagicJack, or most CLECs aren't going to do anything about it. In their minds, 'dial tone is dial tone'.

Ed Vaughn, MBSWWYPBX