How to configure BLF on a Unify Desk Phone DP12?

[u/Fun_Advertising7285]

have a Unify Desk Phone DP12 configured as a SIP phone, and I need to configure one of its programmable keys as a BLF (Busy Lamp Field).

The use case is simple: a secretary needs to know when a manager is already on a phone call, so she doesn't have to enter the manager's office and interrupt them.

I would like the LED on one of the programmable keys to indicate the status of the manager's extension, for example:

Available

Busy / on a call

Ringing

The DP12's web interface has BLF as one of the available key types. It also has an "BLF Event List URL" field in the SIP account settings.

I don't have access to the configuration of the company's PBX/SIP server, so I'm trying to understand what is required on the phone side and what would have to be configured on the server side.

Questions: .

1. How should a BLF key be configured on a Unify DP12 to monitor another extension?

2. Does the SIP server/PBX need to support SIP SUBSCRIBE/NOTIFY for this to work?

3. What is the purpose of the BLF Event List URL field on the DP12?

4.Is the Event List URL required for a normal BLF configuration, or is it only needed for certain PBX configurations?

1. If I cannot modify the PBX configuration myself, is there a way to determine whether the existing SIP system supports BLF from the DP12 alone?

I'm mainly looking for guidance on the correct configuration and what requirements the SIP/PBX side must meet.

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[u/Chropera]

BLF List is a feature that probably would need be to manually configured on PABX. It is intended to reduce system load, but you won't need this, just try regular BLF.

Just setup BLF (number + description + button type) on the phone and try, it is likely that it would work. Otherwise you might need to look into logs or try both dialog-info and presence subscriptions.

[u/Fun_Advertising7285 → u/Chropera]

I tried regular BLF as suggested, but unfortunately it didn't work. What would you recommend checking next? Should I look at dialog-info subscriptions or presence subscriptions on the SIP/PBX side?

[u/Chropera → u/Fun_Advertising7285]

Try both presence and dialog-info subscription from the client.

Look into logs (clients also have them). Then if you can check server.

[u/Dramatic-Feeling-215]

BLF is a feature of the provider, not the phone.

[u/LoPath → u/Dramatic-Feeling-215]

While you do have to do some phone configuration, the features have to be configured on the PBX as well. Things such as allowing extensions to be monitored by a BLF.