[asterisk-users] Detecting answer with an analogue card

[Eric "ManxPower" Wieling]

Stefano Corsi wrote:
> 
>> > I have two TDM2400 card with some 40 FXS modules and 4 FXO modules. I
>> > would like use analogue lines for outboud calls.
>> > How is it possibile to detect ANSWER?
>> you cannot. it's analogue, no signalling is done on it.
>>
>> unless you write dsp routines to detect the right things
>> at the right moment :)
>>
>> if you want exact cdr records, you must go digital.
> 
> There's still something I don't understand: when using a simple modem on 
> an analog line, you get correct answers from the modem: "NO ANSWER", 
> "BUSY", "NO DIALTONE", etc... why is this possible with these TDM2400 
> cards that cost twenty times as much?
> 
> I know that I'm probably missing something... could you help me 
> understand what?

Because the far end sends a carrier tone.