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New Member

does any one know how to use PSTN Telephone line from one side to another

Dear Sir,

I am very glad, that u are reading this message. I purchase 2 router that is Cisco 1751 -4V , with E&M module now what happen I connect that those with my PBX it is working fine any time I want to connect to another side it is very easy … excellent tone voice quality is also very good ..

Now in one office that I have 4 telephone lines but in another office there is no telephone line but the second office want to use that 4 telephone line from 1st office. Is this possible? Can any body tell me? second office can call the 1st office PBX number but they can not dial the PSTN line , that is the problem if any body know this then can u kindly tell me it is possible or not.

If u know then I bag ur help. Looking forward for your kind reply.



New Member

Re: does any one know how to use PSTN Telephone line from one si

Few questions first,

1. Do you have on both sites PBX connected to your 1751?

2. Where the lines are connetd to? The PBX or as extesion.

3. What is the line protocol? Digital, CAS or Analogue?



New Member

Re: does any one know how to use PSTN Telephone line from one si

Thanx that u want to help me .. thanks a lot ..

now I am giving the question answer to u

Ans: 1 # yes i connected the both site PBX connected to my CISCO 1751 Router.

Answer 2. the Lines are connected to the E&M card of the router ... & the PBX has also the E&m Module which is call the Tie Trunk Port. that is attached with the PBX system it has 4 circute from there , 4 lines / cable came out and entered in to the Router E&M port that port call RJ48.

Answer .3# Analog.

if u need any other question then please let me know?

i am giving my problem in more detail way in below if u have time then u can chekc that also

Dear sir I am requesting you to give some time to read my problem what I feel that u can solve this thing …

Now from the very beginning I am telling scenario.

We have 2 office . let give the name of that office one is A and another one is B .

Side A has 4 PSTN connection entered in to the CO port of the PABX system. I request my PBX engineer to configure the PBX system & add & E&M card. & then setup one Cisco 1751 4V it has 2 Ethernet card one is for LAN another one is for WLAN. NM is all E&M. what I did that is I connect that E&M with the PBX system. That means it is a TIE TRUNK.

In the other office that Means in Side B what I Did that is I have another PBX system but in Side B there is no Telephone lines. (PSTN). It is very important that both the office are connected through Radio Link .. & the ping time between them is 10ms/13ms/20ms.

Now my PBX engineer configure the E&M card of the PBX in side B then I connect that with my another Router which is for SIDE B this router is same like SIDE B .

Previously I did not mention that from the Radio Link is connected with the Router in both side & the LAN port is connected with the switch.

Thing is when side A want to call side B then they press 82 to get access the Router E&M Port then they Press Side B router Destination Pattern 7(I assigned that according with my PBX engineer ) then any 3 digit like 111 then it is ringing .. & both the person can talk & the voice quality is also good.

Now when the Side B people want to talk SIDE A ppl then what they do they dial 9 to get access to their router E&M Port then dial the Side A router destination Pattern like 5 (which is given by my PBX engineer.) & dial any 3 digit like 115 . then it is ringing.

Up to this much is ok .. But my problem is some where else.

That is the SIDE B people want to use the PSTN line which is connected with the PBX of Side A. one more thing I forgot to tell that the People in side A when they want to get access to PSTN or dial the PSTN network then they dial 9 to get access . then they got a dial tone which is PSTN dial tone after that they press the PSTN number.

Now when the SIDE B ppl dial 9 then they get access the dial tone of his own router which is connected with that PBX system. Then they press 5 to reach side A then usually they can press the 9 & the PSTN digit …but it is not going… what can be the problem . is the problem in my configuration or with the PBX system or this is the limitation in the E&M card of the router.

I am in very big problem for this reason.. so will u kindly help me for this .. & I am very glad to u that u read this with ur full passion.. & I request u to help me if u can.



New Member

Re: does any one know how to use PSTN Telephone line from one si


From what it seems, I would say it sound more problem of you PBX on the A side. That PBX has to differentiate between call designated to the PSTN and call directed to internal extension.

Just to be on the safe side please use the 'debug VTSP all' on both gw and see that the digits are transformed as you are expecting.

I do not see why you need so many stages calling from B side. To ease on your self you just need to create an access number (like 82 on A side) which will close the circuit and the GW will generate dial tone. From that stage any digits string closed by '#' should be auto forward to the B side PBX.

Once that been received the PBX does the internal routing decision between extension and PSTN.

To ease on your PBX routing try to create unique extension structure differentiating from outside calls:

For example extension number begins with 3xx and outside dialing is either 011 or begins with 1.


New Member

Re: does any one know how to use PSTN Telephone line from one si

Thanx for ur kind efford Yaron .. but can get ur email address so that I can ask u lil more abt it



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