[Tfug] VoIP/PSTN bridges (?)

[Bexley Hall]

Hi Zack,

--- On Thu, 8/30/12, Zack Williams <zdwzdw at gmail.com> wrote:

> This might be useful to help understand terminology for connecting
> analog lines to either analog phones or the phone company:
> 
> http://www.voip-info.org/wiki/view/FXO

Yes, I understand the differences (and "responsibilities")
of FXO/FXS devices.  What I don't know is "colloquial" names 
for *devices* that implement these functionalities.  And,
then, recommendations for *particular* devices worth
exploring (that are *not* geared towards "business" deployments)
 
> You can buy cards that will implement either FXS or FXO
> interfaces, or

Yes, but "cards" depend on PC's.  They are tied to particular
form factors, bus technologies, host operating systems, etc.
This imposes too much on how the rest of the system is
implemented (e.g., what if you wanted to implement the
system using a Mac?  Or, a PDP-11?)

> individual small devices that do so.  

IMO, the smarter choice (for me) are two boxes, each with an
RJ11 on one end and an RJ45 on the other -- such that a crossover
cable between the two would (conceptually, if not in practice)
allow the assembly to replace a "phone cord".

> Costs vary, often greatly
> depending on quality and if the device has a hardware echo
> cancellation unit.
> 
> Nearly all of the non-card appliances talk SIP on the network, and to
> follow up on John's comments, you'll likely be using Asterisk or
> FreeSwitch (which I prefer) or similar to implement the phone routing
> bit.

I think (speaking from *ignorance*) these will probably be too
"application specific" to fit my ultimate needs.  I think they
are probably designed, too much, with PBX-ish functionality
and not enough with their "fundamental services" in mind.

By way of an example, imagine if photocopiers had been implemented
(originally) as "scanners" hardwired to "printers".  They would be
effective photocopiers.  But, useless as scanners or printers.
Their "component services" needed to be exposed to make scanning
or printing feasible.  Then, photocopying could be *reimplemented*
just by wiring the two services together.

I fear the software cited will be too oriented to implementing
a particular type of *appliance* (i.e., a PBX, in much the same
way I describe the photocopier) rather than to providing a set
of *services* (which could be *used* to implement that
appliance -- or any *other* appliance!)

> There is other software that will work as a soft fax (spandsp
> and variants).
> 
> For handsets, it's usually much simpler to get SIP capable
> ones that connect to the network and frequently can be PoE
> powered.  I'm a fan of Snom's phones, but other people like 
> Polycom, Aastra, Cisco, etc.

As I mentioned in my reply to John, I expect to use BT earpieces
for normal phones (since it will be in your ear, anyway).  The
FXS adapter is necessary (instead of a "SIP phone") to interface
other existing "POTS oriented" technology to the system without
having to reinvent the wheel.

E.g., when I wander over to the neighbors' houses, the BT
earpieces are useless.  "Out of range".  So, I want to pick
up a conventional cordless phone, tell the "house" (system)
to enable that interface (i.e., the cordless phone is
normally *not* enabled since it represents a potential
means of gaining REMOTE entry to the system) and then be
able to walk next door knowing that I am still "connected"
to my phone line (if I receive a call or want to make one)
as well as the rest of the automation (that can be accessed
via that phone!).

I don't want to have to design a cordless phone in order to
have this capability.  <grin>  Nor do I want to be tied to
this *particular* make/model cordless phone in perpetuity
(i.e., it eventually dies and needs to be replaced)

And, I don't want to treat the "phone system" as anything
"special/unique".  I can route audio and video to various
places around the house, why should "phone calls" be treated
any differently?  Why should I be *limited* to how the
"phone" interacts with me and the "house" just because it
is an "old concept"?
 
> Just as an FYI, this is a VERY deep rabbit hole to go down.

Zack, I am *so* far down that rabbit hole that this is just
a little "side tunnel"  :>

--don