help with Rotary Phone

Maybe the line with DSL does not have compatible protocol. The rotary phone worked with a line having 48V open circuit, and drew from 6mA to 20mA when off hook (as i vaguely remember it; will measure if you want, as i have a genuine MaBell rotary). You could take a multimeter and measure the voltage between the DSL lines, when all equipment (phones, computers, etc) are disconnected. Then either measure the current when that phone is on the line (or short circuit current). The values you get might be instructive...

The current should be 20 mA or more when off hook.

Is there a low pass filter on the phone line after the DSL splitter? There should be a phone line device that keeps the DSL signals from the phone.

If the above is OK then I think you have a defective phone.

Bill K7NOM

Hey Kurtis,

I Googled this because I have clients with rotary phones (retro they like the ring or like Carrie in Sex in the City ) Suprisingly I came up with this: "Be aware, if you have a wall-mounted phone or an older rotary phone, you must buy a different type of filter." its at

Richard

One data point, for what it's worth -- our Western Electric 302 gets along fine with DSL. Our house has got to be pushing the residental ringer-equivalence limit, with three cordless phones and the WE302.

I'm not sure why the filters would be so load-sensitive. I'd expect the older phones to look more inductive than newer phones with solid-state hybrid networks, but that shouldn't bother the DSL filters. In fact, I'm sort of surprised that DSL hash would make it through the old-school hybrids at all, even without a filter.

-- jm ("We're sorry, the number you have dialed is imaginary. Please rotate your telephone 90 degrees and place your call again.")

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I suspect enough of the near-end ADSL signal is getting past the line filter that it begins to clipped by the limiter device across the earphone. When that happens, the resulting intermodulation products fall into the audio range and are transduced by the earphone.

All phones have limiters (which are by definition non-linear). The purpose of the DSL line filters is lower the amplitude of the DSL signals to the point where they are too small to produce intermodulation products. Remove the DSL filter and you can hear the intermodulation products on almost any phone.

An earlier suggestion, that you install a more effective DSL filter, is a good one.

PF

PF

I have a rotary phone from the 70s or 80s, and it doesn't seem to work with

Kurtis-

PF is probably right about the DSL filter. However, there is another problem with older phones. The microphone element uses carbon granules that are compressed by sound waves so resistance varies as you speak. An AC voltage is generated from a DC bias current flowing through the varying resistance of the element.

The problem is that this is a noisy process. There are various pops and hisses that can occur. It sometimes gets especially bad when the granules become caked. You sometimes can make it better by banging the handset against something hard like a tabletop. This frees-up the carbon granules, making the microphone work better.

Fred