Interesting Experiment With Adsl Splitter

[thinhnghiem]

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 exchange. 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

[JMJones0424]

There's a couple of things going on that you need to understand to realize why you got a busy signal. The busy signal doesn't necessarily mean that the line is busy, it is also used to indicate that the connection has failed.

 

A fax machine sends information over the telephone line in the same frequency range as human voice. This means that you cannot use the same telephone line to transmit a facsimile and to make a call at the same time. ADSL, however, intentionally doesn't use the same frequency range as human voice, so you can use a single line for both at the same time. However, because no electronic device is ideal, there is a possibility of tiny amount of bleed over from the voice range up into the DSL range and vice versa. In order to prevent this, the ADSL splitter box is actually a filter which blocks out the voice range from the DSL side and everything but the voice range from the phone side.

 

So, when you swapped wires and tried to complete a call, which is essentially the same as dialing a fax number, the call could not be completed because the relevant portion of the frequency spectrum was being filtered out of the signal by the DSL filter.

[thinhnghiem]

There's a couple of things going on that you need to understand to realize why you got a busy signal. The busy signal doesn't necessarily mean that the line is busy, it is also used to indicate that the connection has failed.

 

A fax machine sends information over the telephone line in the same frequency range as human voice. This means that you cannot use the same telephone line to transmit a facsimile and to make a call at the same time. ADSL, however, intentionally doesn't use the same frequency range as human voice, so you can use a single line for both at the same time. However, because no electronic device is ideal, there is a possibility of tiny amount of bleed over from the voice range up into the DSL range and vice versa. In order to prevent this, the ADSL splitter box is actually a filter which blocks out the voice range from the DSL side and everything but the voice range from the phone side.

 

So, when you swapped wires and tried to complete a call, which is essentially the same as dialing a fax number, the call could not be completed because the relevant portion of the frequency spectrum was being filtered out of the signal by the DSL filter.

Great, thank you