My Librem 5 with the most basic AweSIM recentl arrived and for various reasons am taking getting up to speed with it slowly. One of my top top priorities is making sure cell service is working as currently expected and what any limitations are since it is incurring a monthly charge. I also want a feel for the current expected situation before contacting Purism support.
I am having 2 main problems.
When I call a number answered by a navigation menu, the dial pad does not seem to generate any signal. That is, the menu doest not respond at all, either waiting “forever” or repeating directions/choice possibilities. I’ve found a number of old threads, but can’t tell whether it has ever worked or is even on a roadmap. Telling me to update without also supplying information about a version that does work is not responsive to this question.
This would be number 1 but it is a bit more complicated and has more than one sub-part. Sometimes a call doesn’t go through and when this happens, sometimes I get a text about “unapproved device”. Purism documents that this is “normal” when “3G activity has been detected”. The phone came presetup for AweSIM (a much appreciated service), including set to 4G only. One thing I tried while playing around was disable mobile data. Does that disable VoLTE? I do know that when I reenable mobile data calls still don’t always complete, even after one or more power cycles and I also sometimes get an “unapproved device” text. I have also had cases where one number reliably answered but another land line with a hardware answering machine which never answered until a friend called it for me and it did. I tried that number later with my Librem 5 and it finally did answer.
I know there are people daily driving a Librem 5 and I want to know how to avoid the problems I am having and whether dislpad DTMF should work after a call has been answered.
I have similar issues as you have, mostly with DTMF tones not working properly with certain services (problem #1).
I do have issues with certain numbers that hang up instantly when I call them, like my bank. I guess this is because the Librem 5 is an unapproved device that I need to call in and whitelist with the services that blocks it.
Back to problem #1 though. Certain services handles the dialpad presses like they should, other services just registers everything as the number one and most services don’t register anything at all and hangs up after a while since there’s no option delivered to them.
I wonder what to do about this. If I should call these services and troubleshoot with them because to me it seems logical that a phone like the Librem 5 ought to support DTMF tones out of the box.
Edit: I live in Sweden and use a Swedish operator called Telenor.
No bank, and no recipient of a call from you can know which device you are using to make the call (except for your mobile carrier, and they see that anyway because it’s how they know your device is authorized to be on their network, courtesy of the SIM). If there’s a problem with call rejection, it would more likely be based on a rejected phone number (VOIP, for instance, or perhaps your Caller ID registers as anonymous or unknown and the entity has a policy of rejecting those). For your situation, maybe you don’t have VoLTE enabled, so the call fails?
EDIT: Well, I suppose it’s not impossible that a spy/police/hacker group with specialized equipment might be able to collate data from various interceptions and sources to deduce or identify your device make, but probably not a bank.
That would be my expectation. We would be talking about significant privacy fail. At least, if your statement is incorrect then I would like to know about it!
Yes, it is possible that rejection occurs by the called party on the basis of the phone number of the calling party but that is a bit crappy as a primary security measure e.g. lost or stolen phone bypasses that straight away.
It is also possible that this is some kind of niche calling incompatibility scenario with the carrier i.e. works most of the time but sometimes fails, and it is the carrier dropping the call (or the phone).
I wonder whether it is possible to fingerprint DTMF. That is to say, I don’t know what the tolerances are in the DTMF specification but is there enough variation in e.g. frequency or duration to fingerprint? It also however depends on whether DTMF is transmitted in-band i.e. as actual tones then compressed by the codec or DTMF is transmitted out-of-band. (Or, following that thought further down the rabbithole, is there enough variation to use DTMF as a covert channel e.g. to send the IMEI? )
Can’t believe no one tried to this guy when he posted…
DTMF never works for me in my work office building. Hell, voice only works sometimes, even though I have 3 or 4 bars and it shows 4G. I assume this is due to many huge metal hangars and many aircraft radiating all over the spectrum. I can walk across the parking lot to another building (away from the hangars and ramp) or drive a couple of hundred meters down the street and voice and DTMF are fine. I must say though that even when DTMF works, there is no audio feedback (I can’t hear the tones). It’s not about the service I’m connecting to, it is a good strong signal with no multipathing or interference.
