The UCM/4G works on 4G (or LTE) networks. It is not able to work in 5G -only networks, but 5G SIM cards can normally work on 4G Phones.
However, UCM/4G makes use of 3G for Voice calls - it does not support VoLTE (Voice Over LTE).
Check the mobile settings on the phone to ensure that LTE or 4G is selected, NOT 5G. for exampkle for Samsung phones, go to Settings > Mobile Networks > Network Mode.
select LTE/3G/2G (autoconnect) or 4G/3G/2G, as LTE is the same as 4G.
Do NOT select 5G
(ignore the Data Roaming button, it does not affect the network setting)
If the SIM card uses VoLTE for voice calls then Voice calls will NOT work on UCM/4G.
To fix this, disable VoLTE on the SIM Card. On a Samsung Phone, go to Settings > Mobile Networks > VoLTE Calls, and Unselect this feature. Note that some phones do not show this setting.
Note that the new UCM/GSMA7608 module supports VoLTE
Also if the SIM Card is 5G, Disable "Use 5G Standalone Networks", and select Network Mode = LTE/3G/2G (auto connect).
Remove the SIM Card from the phone and insert into the UCM/4G. The UCM/4G should now be able to dial out by voice calls
Last edited on Sunday Sep 22nd, 2024 02:16 am by slychiu
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