asterisk users - Feb 2008 - arris tm502g cablemodem FXS ports and zaptel 1.4.8

Hi there,
I have a cablemodem, ARRIS brand, model tm502G. It has two FXS ports.
I was wondering if anyone has details about the correct signalling of
these FXS ports when connected to original X100p.

Tests:
fxsks on the zapata.conf and zaptel.conf files. From my cellphone I
call the ARRIS, it starts ringing but the zap channel sees no call
coming in.
fxsls on the zapata.conf and zaptel.conf files. From my cellphone I
call the ARRIS, it starts ringing, zap channel picks up the call. all
good.
fxsgs on the zapata.conf and zaptel.conf files. ztcfg reports error
about invalid mode.

Well, I used loopstart as the signal, however when using it I face one
very nasty issue. My asterisk/zap channel does not detect hangups
correctly. I have enabled busydetect but it's kind of unreliable.
Specially when using DISA, if one of my external callers use DISA and
the external caller hangsup, asteirsk wont see athing and will keep
both zap channels open.

I will like some suggestions with this as i am not sure if it's
related to signalling in the ARRIS or maybe some tweaking i can do in
the x100p (true x100p).

Thanks,

-- 
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Erick Perez