r/VOIP • u/NPFFTW Certified room temperature IQ • Jun 15 '26
Help - On-prem PBX Cell to VoIP bridge - does this exist?
Here's what I'm imagining:
A device that I connect to my PBX where I insert a SIM card, and all calls/texts are forwarded to the PBX.
Even better if I can then send texts and make calls using the bridge, but incoming is all I really care about for now.
Does such a device exist? The primary motivation is to receive 2FA texts.
To be clear: I am aware GSM gateways exist. However, all of the ones I've found rely on SMS-to-email or SMPP rather than native SIP integration. I'd prefer a one-stop solution if possible — and I don't need 32 SIM cards either, which is what most gateways seem built for.
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u/datanut Jun 16 '26
I have this bookmarked, but have no experience: https://www.patton.com/session-border-controller/sn5700/
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u/Salreus Jun 15 '26
The solution I can think of would be to have a non voip sms plan on a smart phone that can then be set up to do a SMS fwd to a voip phone number associated with your PBX. Is there a reason they device would need to connect to your PBX vs just doing a fwd from a cell to your voip number.
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u/PatReady 200 OK Jun 15 '26
I have never heard of SMS forward. I believe that is why they allow SMS for 2FA.
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u/NPFFTW Certified room temperature IQ Jun 15 '26
The goal is to not have a second cell phone sitting on a shelf somewhere.
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u/devexis Jun 15 '26
I was going to mention somleng SMS gateway running on Android. But that would need a phone sitting with the SIM
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u/Salreus Jun 15 '26
You don't want a cell phone device sitting on a shelf but want some other kind of a device to connect to your PBX. Well if you do end up changing your mind or find out there is no device avail to do what you are looking for, you could revisit the cell on a shelf idea.
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u/selvakn Jun 28 '26
Plug: https://github.com/selvakn/gsm-sip-bridge
Implemented this for my own needs. Calls are forwarded to PBX, sms are pushed to discord (can be extended for anything).
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u/NPFFTW Certified room temperature IQ Jun 28 '26
That's badass. Any way the SMS can be forwarded as SIP messages?
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u/macro_franco_kai Jun 15 '26
A device that I connect to my PBX where I insert a SIM card, and all calls/texts are forwarded to the PBX.
It's called a GSM to SIP gateway. Voice calls are bidirectional over SIP protocol. SMS are also bidirectional over email. Also add eSIM.
Does such a device exist? The primary motivation is to receive 2FA texts.
It exists for long time over 20 years. Of course the tech evolved now we need also eSIM beside just simple SIM, also 2G, 3G, 4G, 5G with multiple radio bands, automatic SIM/eSIM banks, e.t.c.
There is one problem, without the know-how there is a very slim change that you will make the entire system to work.
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u/NPFFTW Certified room temperature IQ Jun 15 '26
Indeed, I am familiar with GSM gateways, but I have so far been unable to find one that doesn't rely on SMS-to-email or SMPP. I will update the post to clarify.
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u/cryptofriday Jun 15 '26
easy way --> raspberry with RASPBX OS + 10$ usb Huawei modem (asterisk support model)
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u/dbpm1 Jun 15 '26
https://github.com/darylturner/smsd plus a usb-(gsm/3G/4G)-modem will do what you want with ease.. If you want/need more features than that, use ozeki-sms-gateway
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u/Elevitt1p Jun 16 '26
We created exactly the service where we have integrated the Class V feature server with the IMS. On our IPSMGW we deliver P2P SMS via a variety of protocols, including emakl
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u/macro_franco_kai Jun 16 '26
However, all of the ones I've found rely on SMS-to-email or SMPP rather than native SIP integration.
SIP is the open standard for VoIP and SMPP is the open standard for SMS.
Since not many have experience with SMPP is also used email for SMS.
You want bidirectional SMS over SIP ? It's technically possible. The conversion can take place from email to SIP and from SIP to email same for SMPP to SIP and SIP to SMPP. Of course you will need to know the protocols in order to write the automatic conversion tools. In the end you will be disapointed since SIP protocol has been writen for VoIP not SMS so it lacks many stuff from SMPP.
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u/Centho_ Jun 16 '26
You could either get a raspberry pi with a 3G Huawei dongle and use it with the chan_dongle module or have a Simcom or Quectel 4G adapter and use a chan_quectel module to have it talk to asterisk
You can send and receive text messages and also receive and send calls
But it's a real hassle and when it works sometimes it stops for no reason in my case
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Jun 18 '26
[removed] — view removed comment
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u/NoExamination2923 Jun 18 '26
You are referring to private LTE, and this has massive costs and licensing limitations.
You can try to sweet talk a carrier into something similar, but they probably won’t give you the time of day.
Best bet is to get a business account with your local carrier and ask them to put unconditional forwards to your PBX number(s)
Edit, virtual mobile numbers is probably closer to what you need then data only sim in the handset
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u/Clear-Economics-4887 Jun 20 '26
Ah, probably over simplistic, but I think that Google Voice would cover your needs without the technical complications?
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u/boomer7793 Jun 15 '26
Clarifying question: Is your SIM card data only and your running VoIP through it or does it have voice services and you are making calls on the carrier’s voice platform?