is wideband good approach for PSTN for voice and fax services

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is that good approach to use wideband for PSTN


i want to design a system which caries Voice and Fax services over PSTN by using wideband channel. the datarate for voice is 28.8kbps,

also i am intrested to use different channels for Fax and voice.

please give me some professional remarks and any helping meterial

Best Regards
 

PSTN networks are only rated up to 3 KHZ!!! The local ends are often 90+ years old and are subject to all sorts of cross talk - mainly dialling induction, mains hum and miscellaneous pops and clicks. Also their attenuation can be extremely variable. Its hard to synthesise these in a lab. Also the PSTN operator will put a limit on your send level, so you don't cross talk with other users.
Frank
 

ADSL works just fine on PSTN lines, they take into account the variable attenuation of the channel by "chopping" it into small pieces and characterise each one.

That said, I doubt your telco operator will appreciate you highjacking their line
 

I measured the round trip frequency response of telephone lines in the city. 3kHz was at -12dB and high voice vowels sounded very muffled. Consonant sounds from voices did not exist. I complained to Bell and they said it was normal and their limit is -15dB!
 

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