Telephone dial noise suppressing

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  #1  
Old 05-09-04, 04:54 AM
wizzard
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Telephone dial noise suppressing

I have a USA phone/Answer machine which I want to use on 220v supply. I used an appropriate voltage adaptor which is ok and I can use the phone. However everytime I dial out, I get a humming noise. If I use a step down transformer (220V to 110V), I DO NOT get the humming. Ideally the voltage converter is the preferred choice as it is much lighter. Any ideas please?

Also, will a ferrite ring help?
 
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  #2  
Old 05-09-04, 07:38 AM
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Please describe the 2 adapters. What are the ratings on each adapter. If they are DC output it could be that the new one is not filtered.
 
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Old 05-09-04, 11:25 AM
wizzard
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Originally Posted by joed
Please describe the 2 adapters. What are the ratings on each adapter. If they are DC output it could be that the new one is not filtered.
The transformer is 85W. The voltage converter that is giving the noise is DC 9V 800mA. This adaptor, is what we call regulated in UK.

What do you mean by filtering? Can this be done with a ferrite ring, say?
 
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Old 05-09-04, 12:38 PM
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2 thoughts -- buy an equivalent power adaptor for the phone in europe -- one that has the right voltage / wattage output for the phone. Then, if you are lucky, plug it in -- but you probably have to cut the wires to the phone and replace the plug with the one that was made for the phone. I've done that when I lived in Germany.

The other idea would be to get a very small transformer -- the phone doesn't take much power -- less then 50 watts. the transformers are pretty small. The voltage adapters that you are using are only good for motors and the like, not good for electronic equipment. Its not surprising that they don't work with your phone. They use a chopping of the signal instead of actually converting it normal 110V AC power. Hope this helps.
 
  #5  
Old 05-10-04, 11:13 AM
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Regulated and filtered are almost the same thing. A regulated supply also has components to keep the voltage constant. Many cheap DC adapters only have diodes in them. They do not have capacitors to filter the dc. It sounds like you may needs better quality regulated adapter.
 
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