I have 5 DP720 handsets hanging off a DP750 base unit, each with their own SIP account and corresponding outgoing line setting for outgoing calls (only 1 line assigned per handset) and each sip account set to HS1, HS2, etc for incoming calls.
On incoming calls our Asterisk 13.8 server attempts to ring all 5 handsets at once using the Dial application.
For some reason, it only rings a random selection of 3 out of the 5 DP720 handsets at once (should ring all 5). The random selection of 3 varies each time and the other two just don’t ring.
I also get SIP retransmission timeouts when this happens.
I suspect this is a hardware limitation of the DP750 base unit, even though it can supposedly support 5 simultaneous calls.
All handsets were reset to factory defaults and the issue persists. They are running the latest 18.104.22.168 firmware
two out of the 5 handsets are running a different hardware revision (1.6A instead of 1.8A for the other 3 handsets).
Can anyone shed light on this?
Is there a way to allocate an incoming call to just two of the handsets for one SIP account? I suspect reducing the number of SIP accounts to 3 might work around this also.