asterisk users - Oct 2005 - TDM04B card with only 3 lines connected using chanisavail

I noticed that using a TDM04B and only having 3 analog lines connected 
at this time (4th is coming)
I was using ChanIsAvail(Zap/4&Zap/3&Zap/2&Zap1) which gives me an 
available line.... no problem.

However Zap/3 did not actually have a line connected at this time. Yet 
asterisk still gave me it as
an option for dialout even though no dial tone or anything....

Is that expected... Obviously I can edit zapata and not use it. but I 
just thought asterisk would
potentially detect no line connected and not even give me it for 
chanisavail?

Jerry

> I noticed that using a TDM04B and only having 3 analog lines connected 
> at this time (4th is coming)
> I was using ChanIsAvail(Zap/4&Zap/3&Zap/2&Zap1) which gives me
an
> available line.... no problem.
> 
> However Zap/3 did not actually have a line connected at this time. Yet 
> asterisk still gave me it as
> an option for dialout even though no dial tone or anything....
> 
> Is that expected... Obviously I can edit zapata and not use it. but I 
> just thought asterisk would
> potentially detect no line connected and not even give me it for 
> chanisavail?
Nope, there is no code to detect an unconnected pstn line. The chipset
has far more capabilities for such stuff then has been implemented,
but obviously those functions have not been addressed. (Note: there
was, and maybe still is, a compile-time option to detect unconnected
pstn lines, but not sure the option still exists.)

Per the chipset spec sheets, the TDM card can detect bridged handsets,
unconnected pstn lines, reverse polarity, and much more. Adding the
code to support that stuff is not a trevial task given the different
country standards that should be addressed, etc.