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Topic Title: Interesting experiments with ADSL splitter
Topic Summary: Some funny experiment with ADSL splitter, which can result in new effect
Created On: 16 December 2013 10:01 AM
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 16 December 2013 10:01 AM
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thinhnghiem

Posts: 7
Joined: 11 December 2013

Experiment 1
As we know, the ADSL splitter box has 1 input and 2 outputs, one for phone signal line, and the other for internet signal line
Plug the telecommunication line into the input. Then in the output lines, I make the swapping. I plug the phone line to the internet output, and the internet line to the phone output
Then I dial the phone to call to a fax number
Surprisingly, I heard the busy tone, instead of fax tone.
Note: When I connect in normal way, plug the phone line to the phone output, and internet line to the internet output, this effect does not happen. That means I heard the fax tone as usual
Experiment 2
I make the looping back from the output to the input. To do this, I cut into the cable and heal the wire inside
Then I make the looping as seen in my attached screenshot

In a), I loop the net output to input, and connect phone output to a telephone machine. No signal at all

In b), I loop the phone output to input, and connect net output to a modem, this time I can access internet normally

Could anybody tell me how to attach screenshot here, so that i can attach the schema for more detail
 16 December 2013 08:41 PM
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kengreen

Posts: 400
Joined: 15 April 2013

I'm puzzled as to the purpose of your experiments?

The "splitter box", usually referred to (wrongly) as a "filter", is properly called a "diplexer". A filter removes something whereas the diplexer simply separates two signals.

The telephone circuit is purely an audio circuit and the telephone output is therefore fed via a "low-pass" arrangement; i.e. it removes everything above the upper limit required for "telephone quality".

The "Internet" output is basically the bit of spectrum which the low-pass filter removed; hence it does not pass anything much under (say) 3 kH.

It appears to me that you have been experimenting with short-circuiting the two separation filters; of course, I could be wrong.!

Ken Green
 17 December 2013 08:58 AM
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ectophile

Posts: 528
Joined: 17 September 2001

All the diagrams I've seen for ADSL filters just show the "broadband" side just wired straight through, with no filtering at all.

This explains how the early models of BT "Home Hub" could also act as cordless phone base-stations. If the Hub was connected to a high-pass filtered line, then the telephone signal wouldn't get through.

(The BT Home Hubs, up to the model 2.0, were designed to work with BT's VOIP system known as Broadband Talk. However, if that service was not available, the phones would revert to acting as normal phones, connected through to the land-line.)

The phone side is low-pass filtered. Ones for the UK market should also have a ring capacitor to ensure that the phone rings properly on incoming calls.

-------------------------
S P Barker BSc PhD MIET
 17 December 2013 09:40 AM
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thinhnghiem

Posts: 7
Joined: 11 December 2013

Originally posted by: ectophile

All the diagrams I've seen for ADSL filters just show the "broadband" side just wired straight through, with no filtering at all.



This explains how the early models of BT "Home Hub" could also act as cordless phone base-stations. If the Hub was connected to a high-pass filtered line, then the telephone signal wouldn't get through.



(The BT Home Hubs, up to the model 2.0, were designed to work with BT's VOIP system known as Broadband Talk. However, if that service was not available, the phones would revert to acting as normal phones, connected through to the land-line.)



The phone side is low-pass filtered. Ones for the UK market should also have a ring capacitor to ensure that the phone rings properly on incoming calls.




Above is the link to see my schema for the second experiment
 17 December 2013 09:40 AM
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thinhnghiem

Posts: 7
Joined: 11 December 2013

 17 December 2013 09:41 AM
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thinhnghiem

Posts: 7
Joined: 11 December 2013

Hi all,

I have submit my scheme to flicker. Can anyone tell me how to post the URL here for more discussion?
 17 December 2013 01:10 PM
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ectophile

Posts: 528
Joined: 17 September 2001

These forums are set to block any attempts by newcomers to post links. That's to deter spammers who just sign up to post links to their products.

The best you can do is to modify the URL so that it isn't actually a URL, but can easily be edited back into one by anyone who wants to see your posts.

-------------------------
S P Barker BSc PhD MIET
 17 December 2013 05:07 PM
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thinhnghiem

Posts: 7
Joined: 11 December 2013

Thank you ectophile

1. The first experiment is found by accident, when I investigated the splitter by swapping the plug in

2. The second one was done by my curiousity. In actual, I cannot guess what happens when I create the looping like this.

My schema for the second experiment can be found in

abc-Link removed/photos/80780504@N07/

(Please remove the prefix abc- to get the real URL for the image)

Anyone can explain the result of experiment a), why I cannot have the tone of telephone
 17 December 2013 05:11 PM
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thinhnghiem

Posts: 7
Joined: 11 December 2013

Again, the URL is removed,

Let's try

flickr.com/photos/80780504@N07/

by adding prefix http://www.
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