Sena Expand Boom User Manual page 17

2. When you have an incoming intercom call during a mobile phone
call, you will hear 4 high tone beeps, alerting you that there is
an incoming intercom call. You will also hear a voice prompt,
"Intercom requested". In this case, the intercom call does not
override the mobile phone call because intercom has a lower
priority than a mobile call. You have to hang up the mobile phone
call to make or receive an intercom call.
6.2.3 Intercom and Two-way Radio
As described in 5.4 of this user's guide, you can use a two-way radio
and Sena Expand Boom Bluetooth intercom simultaneously by using
the Sena SR10, a Bluetooth Two-way Radio Adapter, along with the
Sena Expand Boom. Incoming audio from the two-way radio does not
interrupt an intercom conversation but is heard in background.
Mobile Phone
Mobile Phone
HFP
Pairing
+
A2DP
Audio from
Two-way Radio
Multipoint
Sena Expand Boom
Pairing
Intercom
Intercom
Pairing
Sena Expand Boom
Intercom and Two-way Radio
Expand Boom
Two-way Radio
Wired
Connection
SR10
17