asterisk users - Feb 2006 - asterisk 1.2.4 doesn't detect the PSTN hang up

Hy,

I'm writing from Spain.

I have the 1.2.4 asterisk version and 1.2.3 zaptel version. I've heart 
that this asterisk's version detects correctly de hang up of PSTN, but 
in my case this thing doesn't happen.

Moreover, my asterisk sends the next messages in the CLI:

Feb 21 15:03:13 WARNING[10363]: chan_zap.c:10876 setup_zap: Ignoring 
signalling
Feb 21 15:03:13 WARNING[10363]: chan_zap.c:10876 setup_zap: Ignoring 
answeronpolarityswitch
Feb 21 15:03:13 WARNING[10363]: chan_zap.c:10876 setup_zap: Ignoring 
hanguponpolarityswitch
Feb 21 15:03:13 WARNING[10363]: chan_zap.c:10876 setup_zap: Ignoring 
signalling
    -- Reconfigured channel 3, FXS Kewlstart signalling

What could be happened?

Thanks for all.