When your handset shows you the "Insufficient capacity" error is because the base station reached the maximum amount of calls.
The maximum number of calls manageable by a base station depends on the base type, the operational mode (single or multi cell), the codec used and if SRTP authentication is enabled.
|Snom M300||Snom M700 (single cell)||Snom M700 (multi cell)|
|Max narrowband calls (g711, g729*, g726)||5||10||8|
|Max wideband calls (g722)||2||5||4|
|Max calls with SRTP auth. enabled** (g722, g711, g729, g726)||2||5||4|
Please note that for example if you add 5 handset in a PBX ring group every call to such group will use 5 concurrent calls.
* using g729 with M300 has a known limitation: the maximum number of concurrent calls between handsets registered to the same base is only 4.
** the reduced limit of concurrent call related to the SRTP authentication is applied when SRTP authentication is enabled in one of the configured SIP servers, so if you don't need SRTP authentication, please make sure to disable SRTP authentication on all the SIP servers.