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Direct POTS phone to POTS phone over Internet without using a 'voip provider'

Posted on 2006-06-16
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Last Modified: 2008-01-09
I have two small offices and I would like to have telephone 'extensions' both ways. Simply, POTS phone at office 1 to POTS phone at office 2. The 'PBX' at each location have POTS extension ports. I have unused public IP addresses at each location. What 'black' box will let me plug in a POTS phone into it and the other side is a network (TCP/IP) connection to my internet router. The 'black' box will only be used to 'dial' one IP address ( fixed programmed IP number ? ) at the other office. Same setup at the other office coming back. And a simple setup, just configure a single IP number/address to call automatically ( or press a dial number button) when the phone is off-hook. Same at the other office in the other direction.

POTSa > BOX > ROUTER > INTERNET > ROUTER > BOX > POTSb - and - POTSa < BOX < ROUTER < INTERNET < ROUTER < BOX <POTSb
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Question by:rdfreedman
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by:grblades
ID: 16921800
You could get a Sipura SPA-3000 box and connect its FXO port to the exchanges POTS interface. Then get a normal VoIP phone and configure it to connect to the SPA-3000.
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by:rdfreedman
ID: 16923919
Maybe, to clarify.... POTS port on telephone system connects to box who's port is an IP address from/to internet. Same at the other office. Pickup my extenion (123) phone and dial extenion 106, 106 is plugged/ connected to the box that connects through the internet to the other office and its extension (16) number. Don't want to 'buy phones' and should not need to buy phones... just use existing POTS lines, each office. This way anyone at either office can call any extension at the other office and talk. An inbound (CO) call can be answered and 'parked' on my extension (123) if for me or parked on extension 106, the other office in the other city, waiting for someone there to answer.
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by:grblades
ID: 16923974
If you do that you will need to dedicate a local POTS line for each extension that you would wish to call at the remote site. How many is this likely to be?
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by:rdfreedman
ID: 16926712
The POTS line used is the extension. Not a CO line input to the phone system.

When someone in Office A at any extension 'dials' extension 106, 106 is connnected (always) to extension 16 at office B and can then 'dial' Jim at extension 12 in Office B. Extenisons are tied up and no CO lines are used.

If Jim answers an inbound (CO line) call, Jim (at 12) can transfer it to extension 106 at Office A. Now a CO line is in use at Office B, transferred to Office A via an extension number/line/port. CO in, to 16 across the state to 106. This is how I see it working.
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by:feptias
ID: 16927181
Hi rdfreedman

I understand what you are trying to achieve and some years ago I tried to implement almost exactly the setup you describe using a piece of equipment on loan from a supplier that I was evaluating for the UK market. In principle it is possible using a VoIP gateway device (equipped with an FXO port) at each site, but in practice you will have to look in great detail at the configuration and programming available on that equipment. I don't know the Sipura and the technical specs on their web site really don't go into enough detail to tell. Your best bet would be if you can find a supplier who is willing to sell you a couple of units on a sale or return basis so you can try it and get a refund if it cannot be made to work.

The manufacturers probably only see the FXO port as a way of connecting to the CO line, not as a way of connecting to an extension socket on a PBX. As a consequence the programming options on the FXO port will be based on the following assumed usage:
a) for incoming calls arriving from the PSTN (these probably get routed to the FXS port)
b) for outgoing calls the FXO port is used as a fall back should the IP connection be unavailable or unsuitable

This would not be consistent with what you require, i.e.
a) incoming calls on the FXO port to always be routed to a pre-defined remote VoIP device (i.e. the sipura at the other office).
b) incoming VoIP calls to, in effect, take the FXO connection off-hook giving the caller a kind of DISA service.

If the money you expect to save on call costs is sufficient to justify the time and expense involved, then you could use an Asterisk server at each site. This is highly configurable and would be capabale of providing the routing you want, but if you don't already know the product there would be a considerable learning curve (i.e. cost).
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by:rdfreedman
ID: 17027583
feptias,

Thank you for the input. Building on your suggestion, I contacted Sipura and after several back and forth...

What will do the job, I am told, is their SPA-2100. Has no PSTN port(s), has two FXO ports, has a Ethernet port and can be programmed to 'call' a specific IP from each FXO to the 'mate' IP at the other device, another SPA-2100.

The result, I am told, will be when I pickup, dial extension 106, I will hear the intercom signal at the other office (16) and then can dial 12 for Jim, or 9 for an outside line at the other office. This will work in reverse from the other office B to where I am at, Office A. Cool!

The reason is not to 'save money'. The reason is to have a single inbound 800 number to be monitored and answered at Office A and transfer the inbound call to an extension at Office A or (or) an extension at Office B.

This setup could also be expanded to another office setup in the future, I am told. Just add another device at each location and connect to an open extension POTS port on a telephone system. Not my intent, at this time.

I am working on doing this with a 'new' telephone vendor and will post back when I have results to report. Maybe by October 2006.
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by:feptias
ID: 17035977
rdfreedman

Many thanks for the feedback. I'm a bit worried that the web pages for SPA-2100 describe it as having two FXS ports, not two FXO ports.
http://www.sipura.com/products/spa2100.htm

I know how easy it is to get FXS and FXO mixed up when talking to suppliers. You should certainly check this out again before buying.

My comment about costs balanced with savings may not be strictly true for what you're doing, but decisions about investment in technology nearly always sink or swim based on the cost. I should have said that you would have to balance the cost of your time learning how to build, configure and maintain an asterisk based solution against the benefits of having that solution. If there isn't a boxed off-the-shelf solution available to do what you want (e.g. from Sipura) then your remaining options are potentially expensive either in terms of time or money or both.

Please keep us updated on progress, even if the question gets PAQ'ed.
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by:grblades
ID: 17035992
The SPA-2100 has FXS ports which are designed to be connected to telephone handsets. FXO is used to connect to a PSTN.
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by:feptias
ID: 17036044
grblades

What the questioner is trying to do (as far as I can see) is to connect an FXO port to an analogue extension socket on a legacy PBX:

Local user -> PBX extn1 -> Office1 PBX -> PBX extn2 -> Sipura -> VoIP/Internet -> Office2 (similar setup to 1)

Where PBX extn1 is a phone handset, but PBX extn2 is just a cable connecting the Sipura FXO port directly into the wall socket for extn2 (no handset). This should work because electrically a PBX extension socket is virtually the same as a wall socket for an incoming PSTN line.

Unfortunately, manufacturers like Sipura don't seem to be able to think "outside the box" and can only imagine an FXO port being connected directly to the PSTN. If you connect it to the PBX extn port instead then it has the potential to provide an extremely flexible solution, both for incoming and outgoing calls, on legacy PBX's.
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by:rdfreedman
ID: 17036990
OOP's.... FXS is correct. the SPA-2100 has these. I found these definitions at answer.com:

FXS
Foreign exchange station
A Foreign Exchange Station, or FXS, is a telephone interface which provides battery power, sends dialtone, and generates ringing voltage. A standard telephone plugs into such an interface to receive telephone service. A telephone exchange is an example of an FXS.

In a nutshell
FXS is any device that, from the point of view of a telephone, seems to be a telephone exchange. As such, it should be able to supply power to the connected telephone, provide ring signals and dialtone, understand when phone goes on-hook or off-hook, and send and receive voice signals.

FXO
Foreign exchange office
A Foreign Exchange Office, or FXO, is a telephone interface that receives POTS, or Plain old telephone service. It generates the on-hook and off-hook indicators used to signal a loop closure at the FXO's end of the circuit. Analog telephone handsets, fax machines and (analogue) modems are FXO devices. FXO interfaces are also available for computers and networking equipment to allow these to interact directly with POTS systems. These are commonly found in devices acting as gateways between VoIP systems and the PSTN.

The FXO must be connected to the Foreign exchange station interface, or FXS interface. The FXS interface delivers the familiar dial tone and ring tone to the FXO and supplies the power for the FXO device to work.

In a nutshell
FXO is any device that, from the point of view of a telephone exchange, seems to be a regular telephone. As such, it should be able to accept ring signals, go on-hook and off-hook, and send and receive voice signals.

I read the above as... The FXS is what a telephone instruments plugs into and the FXO is the telephone instrument itself.

If I translate the above correctly, the device should behave as a FXO device port to connect to the telephone system's POTS (FXS) two wire port.

The SPA-2100 is not the right device that I should be looking for.

For what I want to do, two extensions at each office, I need a 'box' with two FXO ports and one Ethernet port pointed to the other office's two IP addresses and one LAN port to be able to program the darn thing. Same in the reverse direction, i.e., the other office.

The device needs to 'look like' a POTS phone connected to the telephone system.

Do I have this correct now?
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grblades earned 250 total points
ID: 17037052
As in my first post you will need something like the Sipura SPA-3000 which has a FXO port (aswell as a FXS port).
You will need a pair of these devices for every phone that you wish to link between locations.
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Assisted Solution

by:feptias
feptias earned 250 total points
ID: 17037127
Yes you have it correct. An FXO port on the Sipura can be connected directly to a spare POTS 2-wire extension port on your existing PBX.

While the Sipura-3000 does indeed have an FXO port, I would be very surprised (albeit pleasantly surprised) to find that this device could be programmed to behave the way you want. This is because FXO ports on VoIP gateways are designed to be connected to the PSTN, not to an extension port on a PBX. It is therefore unlikely that the dial plan in the Sipura will permit the routing of inbound VoIP calls to the FXO port and also unlikely that inbound calls arriving at the FXO port can be routed to a remote IP device.
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Author Comment

by:rdfreedman
ID: 17082136
Thank you, grblades and feptias.

We learn as we go. it will be several months before this information can be verified, by testing and a bit of trial and error. I'm going with and working with Bellsouth (Florida, FLL & ORL) for the equipment and installation of this and updating lines, 800#'s, etc. I will post back to here, the results.
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