GXP-2020 / Asterisk - BLF on outbound calls

[unitron]

Hello,

I have a couple of grandstream gxp-2020 phones and an asterisk server. I am slowly getting the phones working the way i want but have a problem with the BLF function.

After alot of trial & error, i've got it working for inbound calls but it does nothing for outbound calls. It i make a call from phone1, the blf light stays green on phone2. However, if phone1 recieves a call, the light on phone2 flashes red / goes solid red as it should.

Below is an except from my config as it is at the moment. (the sip config is identical for both phones so i've only pasted 1 to keep the length down).

{sip.conf}
[general]
context=default
allowoverlap=no
allowtransfer=no
bindport=5060
bindaddr=0.0.0.0
srvlookup=yes
jbenable=yes
subscribecontext=blf
notifyhold=yes

[230]
context=main
type=friend
username=231
secret=sip123
host=dynamic
nat=no
callerid="Phone 1" <230>
mailbox=230
call-limit=6
busy-level=1
allowtransfer=yes
allowoverlap=yes
limitonpeer=yes

{extensions.conf}
[blf]
exten => 230,hint,SIP/230
exten => 231,hint,SIP/231

{output of show hints}
-= Registered Asterisk Dial Plan Hints =-
231@blf : SIP/231 State:Idle Watchers 1
230@blf : SIP/230 State:Idle Watchers 1

The 'show hints' output above shows 'State:Idle' for both phones even if one of them makes a call, which I think is causing the problem. You can see that both hints are being watched (the 2 phones are watching each other).

I'm hoping its a simple fix to make the phone register as busy when making a call but i've spent hours & hours over the past couple of days trying every config option mentioned on the web i can find with no luck.

Any help would be appreciated.

Thanks,
Matt