The Dial Tone used in Australia
Dana Troxel
continuous signals. The ITU-T series E.180 supplement 2 lists dial
tones used in most countires. The Australian Dial Tone is listed as
425x25 Hz which means that 425 Hz is modulated by 25 Hz. What is the
resulting dial tone? If 425 Hz is multiplied by 25 Hz you will get a
dual frequency dial tone of 400 Hz + 450 Hz. But I am wondering if in
the implementation of the modulation you are left with the carrier of
425 Hz as well which means the Australian dial tone is made up of 3
frequencies (400,425 & 450). Can anyone help me understand the land
of down under?
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Alan Fowler
>The dial tones of most countries are either single or dual frequency
>continuous signals. The ITU-T series E.180 supplement 2 lists dial
>tones used in most countires. The Australian Dial Tone is listed as
>425x25 Hz which means that 425 Hz is modulated by 25 Hz. What is the
>resulting dial tone? If 425 Hz is multiplied by 25 Hz you will get a
>dual frequency dial tone of 400 Hz + 450 Hz. But I am wondering if in
>the implementation of the modulation you are left with the carrier of
>425 Hz as well which means the Australian dial tone is made up of 3
>frequencies (400,425 & 450). Can anyone help me understand the land
>of down under?
Dana,
Dial tone is 425 Hz amplitude modulated 125% with 25
Hz. I know the AM fraternity will claim that is impossible,
but you van do anything if you do it software instead of
using a real modulator.
If you examine the waveform carefully, you see that
the phase changes sign at about 20% of the maximum amplitude
instead of being clipped at 100% . The result is a very
funny looking and sounding waveform. i haven't attempted to
work out the hsrmonics.
It is rumoured that the contract called for at least
90% AM and the supplier made sure he met the spec.
I have a wave file somewhere and I will post in a
day or two.
regards, Alan.
Dana Troxel
information I have come across since I started this quest. I would
very much appreciate the wave file if you can locate it.
amfo...@melbpc.org.au (Alan Fowler) wrote in message news:<3b3bc67...@news.melbpc.org.au>...
Heywood Jaiblomi
>If you examine the waveform carefully, you see that
>the phase changes sign at about 20% of the maximum amplitude
>instead of being clipped at 100% .
I thought the dial tone in Austraila was modulated counter-clockwise.
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Alan Fowler
>amfo...@melbpc.org.au (Alan Fowler) wrote
>
>>If you examine the waveform carefully, you see that
>>the phase changes sign at about 20% of the maximum amplitude
>>instead of being clipped at 100% .
>
>I thought the dial tone in Austraila was modulated counter-clockwise.
>
I think you will find, if you make a detailed study
of a map of the universe, that the South pole of the earth
is the one pointing upwards.
regards, Alan.
Dana Troxel
Alan Fowler sent me a wave file of the Australian dial tone (Thanks
Alan) and I pulled it into Mathcad and analyzed it with the following
results (dB is relative to the strongest spectral component):
375 Hz: -20 dB
400 Hz: -4 dB
425 Hz: 0 dB
450 Hz: -4 dB
475 Hz: -20 dB
No other spectral components appear to exist or were in the noise.
Throwing caution aside I will take a parting hack at the regulatory
folks OutBack and say that was a blunder by the boys DownUnder :).