On 08/09/2016 01:58 PM, Ralph Mowery wrote:

Try measuring the voltage on the phone line. I don't recall what it
is,but it will be a high DC voltage (still less than 100 volts DC) and
drop to a lower voltage (maybe around 8 to 10 volts) when you pick up
the phone and get a dial tone. When the phone rings there is about 100
volts on the line during the ring tones.

Then compare those voltages to another phone line in another house.

Hello, and not a bad idea. IIRC the Western Electric/Bell standard uses
48 VDC (central office battery) and a ringing voltage of 85 VAC. So
on-hook we should see nominally 48 VDC and off-hook would be variable
depending on central office-to-subscriber set loop losses when DC line
current is drawn. So there might be a situation where there's enough
line current to operate the DTMF pad and produce noise in the receiver
but not enough current is being drawn to signal a normal off-hook
condition with the resulting dial tone. Just speculation. Sincerely,


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J. B. Wood e-mail: