pjsip ограничение линий

Как правильно в pjsip ограничивать колчество линий на endpoint. Вроде как есть параметр endpoint/devicestatebusy_at, но почему то он не отрабатывает.

[main-template](!)
type=wizard
transport=transport-udp
accepts_auth = yes
accepts_registrations = yes
aor/qualify_frequency = 300
aor/max_contacts = 1
inbound_auth/auth_type = userpass
endpoint/disallow = all
endpoint/allow = alaw
endpoint/dtmf_mode = rfc4733
endpoint/deny = 0.0.0.0/0
endpoint/context = city_out
endpoint/direct_media = no
endpoint/device_state_busy_at = 1
endpoint/language = ru

[2222](main-template)
endpoint/callerid = <2222>
endpoint/permit = 10.0.30.140
inbound_auth/username = 2222
inbound_auth/password = password

При звонке вижу смотрю

 pjsip list endpoints

 Endpoint:  <Endpoint/CID.....................................>  <State.....>  <Channels.>
==========================================================================================

 Endpoint:  2222/2222                                      Busy          1 of 1

При втором звонке

pjsip list endpoints

 Endpoint:  <Endpoint/CID.....................................>  <State.....>  <Channels.>
==========================================================================================

 Endpoint:  2222/2222                                      Busy          2 of 1

Где то что то надо еще включить???