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I want to have one stationary device like an android phone that can use a standard local SIM card and forward all calls to a second device over some kind of VoIP protocol. When someone calls the phone number of the stationary device, I want my second device to ring and handle the call through something like linphone, element, or whatever. Ideally, it should be possible from the second device to initiate a call from the stationary device's phone number as well. Bridging SMS too would be nice, but I already have a solution for this on android.

There are many use cases like

  • when traveling abroad, being able to bring the latter device and receive/make calls via the stationary device at home
  • forwarding multiple phone numbers to a single device and e.g. switching off the work number when away from work
  • having privacy when the location of SIM cards is logged, by making calls over wifi from somewhere else than the stationary device
  • when traveling somewhere with bad mobile coverage but available wifi, without having to think about how the second device handles it

Are there any existing projects for doing this?

If not, then what would be necessary to make something myself? Is the best solution something like connected an android device by bluetooth to something running asterisk like was discussed here? Or has something changed in the past 11 years, maybe the existence of some working linux phones makes this possible on a dedicated purism or pinephone device?

Christos Koninis
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anon89816273193
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  • Hello, I think you shoud look at this project https://projects-raspberry.com/call-text-using-raspberry-pi-gsm-module/ and then install a Voip software under the same raspberry pi. You need to write a small programme that should be trigered when you received a phone call and redirect the audio device (/dev/some_speaker_device) to the audio input of (mic) of your voip. You may need to configure and audio mixer (like pulse) to emulate a new mic and new speaker. You may also need to use an ffmpeg lib to decode/encode audio. Now you bridge will work in one way, you need to write the other way – hzrari Aug 12 '22 at 22:31

3 Answers3

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I think you can achieve this with Brekeke SIP Server. I am using their solution to achieve something similar to what you want to do.

ccs_2000
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there are multiple ways to achieve it technically, but the most practical solution to your use case will be to use a VOIP Gateway device. Actually we can not use a mobile phone as gateway between SIM and VOIP calls. so you can buy a voip gateway example GOIP (single SIM) and put your sim, connect to your home internet and configure. your phones softphone (eg linphone) will be able to directly register on it and you will be able to make/receive calls and sms. there will be a new problem as mobile OS platforms are more and more restrictive about power, your sip client will not be able to receive calls while in background for that you will need push, so you can use twillio's mobile sdk to make a client that works fine then forward your calls to twillio from gateway. since there is no number or telecom services involved, cost on twillio should be minimal.

walidabul
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  • This does not provide an answer to the question. Once you have sufficient [reputation](https://stackoverflow.com/help/whats-reputation) you will be able to [comment on any post](https://stackoverflow.com/help/privileges/comment); instead, [provide answers that don't require clarification from the asker](https://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead). - [From Review](/review/late-answers/32015299) – Omkar Jun 16 '22 at 12:53
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A more common way to do this is with an operator service, rather than implementing it yourself.

The operator is able to see the routing to your number and simultaneously call multiple numbers you have set up. Different operators will have different names and details so you would need to speak to your local operator.

For example BT in the UK (who I have no affiliation to - just an example) provide a service called 'Follow ME': https://support.ringcentral.co.uk/s/article/9010?language=en_GB

If you do want to do it yourself than an open source PBC like Asterisk is indeed a good starting point.

Mick
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