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FXS port used with Cellular Basestation Ericsson W35

Level 1
Level 1

A few years back, when CCM 4.3 was around, I had to convert a celluar type basestation into an analog gateway for some IP phones on our companies network.  This was out in Iraq, so land lines were out of the question.

I got this working, but I believe I was using a MC3810 w/ an FXS port and running H.323. 

For my lab, I ordered an Ericsson W35 cellular base station and bought a cheap prepaid SIM card to put in it.  I figured it was another was to get access to the real PSTN.  I am trying to get this to work on a 2801 running CME.  The basestation is connected to an FXS port.  I swore I used an FXS port in Iraq, but I am starting to think that it might of been an FXO (because I cant get this working).

Basically, my goal is to have all my IP phones use it as an outbound gateway, and also users from the outside can call the number assigned to the SIM and it can be translated to hit a hunt-group or however I want it to work.  The part I am having trouble with is just getting it to work with inbound or outbound calls.

I believe the problem boils down to is that the FXS port is always in an Off-Hook status because its connected to the basestation.  I have tried different signaling methods, connection methods (tie-line, trunk), etc.  I cant get it to work.  I get a fast busy as soon as the IP phone finishes dialing the number because that port is already Off-Hook and busy.

Is there a way to accomplish this with an FXS port?  There isnt any kind of configuration methods on the Ericsson device, I already looked at the web gui and its all very basic.  It works fine when I plug an analog phone directly into it.  But when I plug the line into an FXS port on the 2801 I cant get it to work.

Any ideas for configs?

5 Replies 5

paolo bevilacqua
Hall of Fame
Hall of Fame

The cellular interface is most likely FXS, meaning you have to use an FXO. That should be indicated in its documentation.

The documentation doesnt say much about it, I am kinda using it in a different manner.  Althoug... it does have 3G and is a access-point (has ethernet ports).. I wonder if it would be a supported SIP gateway. 

The last time I got this to work was using MGCP to control the port.  This time its connected to a CME router, so I am trying to get this work via cli and H323.  I dont have a VIC2-2FXO, only a VIC-2FXO which doesnt work in the 2800s so I can try it on my lab until I get a few pieces in this week.

Really the logic is the same as many people going with backup cellular data lines instead of the DDR days of ISDN BRIs, only this is using voice.  If I somehow can get the FXS port on the router to stay on-hook until a call arrives at the basestation which will signal the port to go off-hook...then it would work perfect.

An FXS port can be configured to tie directly into a PBX, it doesnt always have to plugged into a phone, fax, etc.  There are the trunk and tie-line commands for that.  I think I am just missing something for the FXS port to go ON-Hook when a call is not comming in.  Then when a call is sensed, it can use plar to ring a number of a hunt group or shared lines, whatever. 

I could just register it to my CUCM cluster as an H323 gateway and see what happens.

As mentioned above:

The Ericsson W35 includes dual POTS interface (FxS)

Not sure where you are getting at with:

Paolo Bevilacqua wrote:

As mentioned above:

The Ericsson W35 includes dual POTS interface (FxS)

I know it has two FXS interfaces, one is for an analog phone, and the other is supposed to be for a fax. 

However, there has to be a way to use this as an analog gateway for your entire CUCM or CME environment.  Like I said, I have gotten it to work with CUCM before, but now I am trying with CME. 

In its current state I have one 7961 registered to CME and one analog phone connected to one of the FXS ports on the same router, they call each other fine. 

Now I am just trying to get them to use this cellular device as a way to place and receive inbound calls from the PSTN.  The GUI for the device doesnt have any sections to modify the telephony side of it, its very plain.

So will I need an FXO interface, or is there a way to use an FXS port in this situation?

So will I need an FXO interface, or is there a way to use an FXS port in this situation?

As answered already in my first reply.

Note: must use CLI for configuration.