It looks like the X101P clones I bought from eBay are dogs, so I'll
look into buying some FXO-SIP box instead. Hopefully, I won't have the
same problems with static, or caller ID and call termination not being
detected.
Still, considering the number of people having similar problems with
those cards, I was wondering what the problem is. Is it because the
hardware, no matter what is advertised, is actually not identical from
card to card so the zaptel driver doesn't work reliably unless they are
among the few remaining authentic cards made by Digium before it stopped
manufacturing them? Because they're actually voice softmodems, and
hence, very sensitive to the computers in which they're installed
(voltage on the PCI slot, sharing IRQ's, etc.)? Other reasons?
The X100P-style cards were never manufactured by Digium; they were
simply analog modem cards that happened to use integrated circuits with
some voice encoding/decoding functionality. The card was manufactured
overseas using a chipset from Silicon Labs, and were fairly popular back
in the pre-broadband analog-modem days. Digium wrote the asterisk
drivers to take advantage of the functionality within the chipset.
The Silicon Labs chipset used on the card was designed to meet US
Telephone standards, and several competing analog modem manufactures
designed their cards using Motorola, Intel, and/or other chipsets. Each
chipset has its own unique driver requirements in terms of initializing
the chips, moving data, timing, etc. Also keep in mind the card designs
were mostly completed back in the days of PCI v1 standards.
Some of the cards sold on Ebay are those that use the Silicon Labs
chipsets while others are obviously based on the Motorola chipset. The
two are not interchangeable without modifying the asterisk drivers.
As mentioned, the Silicon Labs chipset used on the card were
manufactured to US telephone standards (eg, 600 ohm impedance). Other
countries have different standards (guessing, maybe 30-to-50 different
telephony standards), and attempting to use the x100p in those
environments represents electrical mismatches resulting in echo, no
callerid support, and many other objectionable or non-working conditions
(depending upon exactly which country you were in).
Are some of the Ebay ad's misrepresented? Probably.
You're likely to become just about as frustrated with the fxo-sip
gateway boxes on the market. Expensive ones have excellent echo
cancellation while the cheaper ones are rather poor (or unusable). Some
will accept incoming pstn calls while others basically only support
outgoing calls (intended for certain failed conditions). Some are
targeted for the US market (telephony standards) while others support a
larger subset. Some work well on long pstn loops while lots of them
don't work very well at all.
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