[Asterisk-Users] Why echo occurs

[Steve Underwood]

Steven Critchfield wrote:

>On Fri, 2005-02-11 at 15:05 +0800, Steve Underwood wrote:
>  
>
>>Steven Critchfield wrote:
>>
>>    
>>
>>>On Fri, 2005-02-11 at 15:35 +1100, Eric Bishop wrote:
>>> 
>>>
>>>      
>>>
>>>>2. Is only a problem in 2-wire technologies (ie analog and BRI ISDN lines)?
>>>>   
>>>>
>>>>        
>>>>
>>>It is just an analog problem. That is why a BRI can actually transmit
>>>direct digital data instead of audio data. 
>>> 
>>>
>>>      
>>>
>>There is enough spill from the earpiece to the mike on most phones, that 
>>EC is required even on a digital phone.
>>    
>>
>
>Fine, but to get an earpiece, you make an analog portion of the link
>unless someone has made some digital ears with direct data jacks on the
>side of human heads.
>
>So if you say that a SIP handset is like a 4 wire set, and BRI is like a
>4 wire set, and asterisk doesn't mix the ins and outs, you effectively
>are 4 wire through the portion you can control. The remote side is up to
>whoever you call. 
>  
>
What you said was not actually wrong. However, 9 out of 10 people 
reading it will see "echo is something that affects only analogue 
phones". People keep saying this. Its even in comments in the * source 
code. Its wrong.

Regards,
Steve