Telephone Line to Soundcard - Need Help

Obviously, there's no isolation. The PC ground connection hoses your phone line.

That "barrel" most likely contains a transformer.

...Jim Thompson

Which reminds me. Does anyone have specifications on the transformer...

RS 273-1374 ??

Thanks!

...Jim Thompson

If you are into making things yourself, here is the schematic and (very short) bill of materials:

Scroll down to the middle of the page.

Good luck!

-- Dmitri Abaimov, RCDD

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That is an obsolete part number Jim. Use either RS 208-822 or 196-959 (latter is my preference).

Oh come on! Some of us like to do special twists and turns to improve usable bandwidth. I can guess at it, but it's easier when I have facts.

...Jim Thompson

A quick check on the RS site for those part numbers jumps to manuals, but shows nada :-(

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

You could always get one and measure it. They do still make real test equipment, don't they? ;-)

Good Luck! Rich

Oh come on. This 600-600 stuff is STANDARD telephony isolation transformer. It's got 1:1 ratio, and you don't need to know much about its inductance, just put it accross the line, with a 200nF 400V capacitor to filter out the DC part of the telephone signal. These transformers are readily available, in very small packages, easy to use.

The US equivalent has nothing. Did you forget I was on the west side of the pond ?:-)

...Jim Thompson

Jim, come now...

Go to

and type 196-959 into the entry box on the top left of the page and hit GO.

Voila! you get a listing of all the 600:600 line isolation transformers.

Well, I am on the west coast of Australia and I had no difficulty in locating the product. You obviously know that RS Components is based in the UK, and because the US representative of RS may not stock all of the parent company's catalogued products, they can nevertheless get them in from the UK. If you don't see it on the US website then look at the parent company's website.

The same thing happens on the RS website in Australia so when I want an item not shown in the Aus catalogue, but I know it is in the UK catalog, I ask them to get it in from the UK. After all, most of the items in any country's catalog are shipped from the parent company, so its not as if a special shipment has to be made - it just comes in with the next order. If I had wanted this particular transformer myself I could have obtained it from the local RS Components branch since it is also listed under the same part number in the Aus catalog.

You have to think laterally, and not all things are centred around the US....