[Asterisk-Users] Reccomendations for connecting to 3-4 PSTN lines?

[Rich Adamson]

>    I'm looking to connect Asterisk with three (four in the future) PSTN
> lines, and would like to get some opinions on the TDM400 Digium card, vs.
> sip gateways like the Mediatrix 1204, vs. other hardware solutions I'm not
> yet aware of.
> 
>    I need the ability to prioritize which PSTN lines are used for outgoing
> calls (I understand this can be done with the Mediatrix --
> http://lists.digium.com/pipermail/asterisk-users/2004-February/035926.html),
> and only answer two of the three lines (the third line will be answered by
> a directly connected FAX machine, but we can use that line for outgoing
> calls if the first two PSTNs are in use).
> 
>    Does the higher cost of something like the Mediatrix ($634) bring
> advantages to the table over the TDM04b ($337)?  Does the TDM card provide
> functionality which the sip gateways do not (e.g. incoming / outgoing call
> progress)?
> 
> I appreciate hearing from folks who have experience with both methods of
> connectivity,

I wrote the posting referred to above and its been a while since I've
touched the 1204, but here are a couple of comments based on the
firmware that was available at that time.

Mediatrix 1204:
 - box was designed to work with the 1104 as a toll-bypass solution,
   therefore it does not implement many sip protocol functions
 - it functioned very well, good echo cancellation, audio quality, etc.
 - can only be configured via snmp (no telnet, no web). Their configuration
   tool _must_ match the version of firmware, therefore for each firmware
   upgrade you have to remove and reinstall a new config tool (Win32 based)
 - their snmp implementation had no security, therefore one should not
   expose the box to the internet (eg, hacking)
 - each firmware upgrade is a chargable item (not free) and support is
   basically limited to whatever the reseller can provide (usually not
   much help). Very limited help on this list as there aren't very many
   of these implemented with asterisk.
 - it does not implement the sip "register" function, therefore no way
   to know when the box might be unreachable (for whatever reason)
 - documentation sucks unless you are very familiar with reading snmp
   mib variables, translating their language into telephony and * words,
   etc. Very steap learning curve, but once working, pretty solid box.
 - a little company research (in 2004) suggested the company was having
   financial problems, therefore the only valid assumption one can make
   is they may not be around in the long run.
 - I never did test modem use through the 1204, so no idea if faxing or
   point-of-sale devices will work (or how well).

Digium TDM card:
 - works fairly well for pure voice use, but quality of echo cancellation
   and audio is below that of the Mediatrix (and most other comparable
   fxo devices)
 - don't even think about using spandsp or any other modem-based audio
   through the TDM
 - the latest TDM card revision is rev H. Ensure that is the _only_
   revision shipped to you (many resellers have earlier revisions in
   their stock and most of those are prone to failing every week or
   two requiring a reboot or driver reload)
 - software support for the TDM is almost non-existant from digium and
   from the various * lists (there are only a very small number of
   technical people that understand the drivers, etc, and most won't
   touch them.)

Sipura spa3000:
 - slightly more costly then the TDM card
 - audio quality and echo cancellation about the same as the TDM card
   but below that of the 1204
 - somewhat difficult to configure as there are tons of options that
   are not very well documented, and some options are not fully
   implemented 
 - highly flexible in exactly how you want the fxo and fxs ports to
   be configured and inter-operate with asterisk (most generally 
   limited by your understanding, skills, and the amount of time
   available to experiment)
 - historically, more stable then the TDM card
 - if you think through the US E911 and legal issues associated with
   liability for comm failures, the spa3000 will likely win over 
   any fxo device on the market today for soho environments.
 - much easier to diagnose pstn line problems if you have the skills
   and background to understand what its telling you
 - support sucks and is limited to the reseller (or voxilla.com forum
   users)
 - if you've been around Cisco's internal agendas, there is a high
   probability the sipura devices will improve over time.
 - early boxes seemed to have power issues (high heat generation,
   early failures, wall-wort issues, etc). Later versions seem to
   be fine.
 - fairly good international support (eg, tones, ringing, supervision)
   but probably still needs more work for some country standards.
 - I haven't spent any time testing modem use through the box, so
   no idea how well it might function.

The voip market-space is not well covered in the one-to-five pstn
(fxo) line areana. Above approximately four lines, a channel bank
(with T1 card) is likely to be more cost effective when ongoing
client support and satisfaction is factored into overall costs.

Hope that helps....

Rich