Sena Bluetooth SMH5-FM v1.3 User's Guide - Manual (Page 16)

English
SMH5-FM
17
5. The intercom pairing queue is ‘Last-Come, First-Served’. If a
headset has multiple paired headsets for intercom conversations,
the last paired headset is set as first intercom friend. The
previous Intercom friend becomes second intercom friend, and
third intercom friend.
Note:
For example, after the pairing procedures listed above, headset D is the
first intercom friend of headset A. Headset C is the second intercom
friend of headset A, and headset B is the third intercom friend of headset
A.
9. PAIRING WITH OTHER SENA HEADSET
MODELS FOR INTERCOM CONVERSATION
The SMH5-FM can be paired with all other Sena headset models
such as the SMH10 and the SPH10 for intercom conversation. Please
follow the same procedure as above to pair with these headset
models.