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Target release	1.0
Epic
Document status
Document owner	Alexander Feldt
Designer	Zsolt Erdei
Developers	Clemens Cramer
QA	Tita Petre

Goals

Align BLF and Extension behavior for PFKs on Snom desk phones by using XML definitions instead
- Improve user experience
- Improve performance

Background and strategic fit

BLF is a valuable feature for Snom customers, like enterprises who are looking to assist in connecting their customers to a live, available person as well as save business phone use time. Overall, it enables businesses to streamline their communication and better serve customers. BLF aka Extension monitoring has been utilized in numerous ways by businesses using Snom phone systems with multiple extensions. The current implementation appears to be kind of duplicated, but with a few little differences and erroneous behaviour.

Assumptions

Use case#1: A secretary's phone shall display the call status of the boss's line, allowing the secretary to know whether the boss is on a phone call or not. This will enable the secretary to make the decision to put the new caller on hold or let them through to the boss.
Use case#2: Call centers and customer support groups have also a need for BLF: it enables employees to see if their colleagues are free to take a support call or if their supervisor is on another line and unable to help another customer.
Use case#3: BLF is needed by teams working on a specific project: supervisors can monitor team members' extensions and vice versa so all team members are aware of each other's current status.

Requirements

#	Title / Requirement number	User story / functionality	Importance	Notes
1	BLF-XML-01-00	On D8xx series, any PFK (physical or virtual programmable function key) can be assigned to a function, which allows monitoring the state changes of another SIP extension. This function shall be called "BLF-XML"	Must Have	This means, that each PFK of the User Agent (UA, here Snom D8xx) becomes a subscriber of state changes of the assigned SIP extension on another Server (SRV)
2	BLF-XML-01-02	If such SIP extension is configured on other Snom phones in the same SIP domain BLF shall work transparantly without the need of an IP PBX.	Must Have
3	BLF-XML-01-01	The assignment shall be configured either manually via web user interface (WUI) and/or phone user interface (PUI), and automatically via auto-provisioning (HTTP/TFTP setting server), SRAPS, or remote management (TR-069).	Must Have
4	BLF-XML-02-01	On D8xx series, during an active subscription, state changes of the monitored SIP extension shall be visualized on both, PFK LED and PFK label. The PFK label is composed of 3 areas: Label icon, name, and state	Must Have
5	BLF-XML-SRV-02-02	If the SRV (Snom phone) goes into State "Idle", a NOTIFY message shall be sent to the UA, and the following information in its XML body: switch off the assigned PFK LED display the label icon "idle", the label name "name" or "number", the state "idle"	Must Have
6	BLF-XML-UA-02-02	If the SRV (IP-PBX or another Snom phone) is in State "Idle", the UA shall switch off the assigned PFK LED display the label icon "idle", the label name "name" or "number", the state "idle"	Must Have
7	BLF-XML-02-03	In case the notifier being an IP-PBX or another Snom phone: Ringing state => PFK LED blinking fast (colour?), PFK label & icon "ringing"	Must Have
8	BLF-XML-02-04	In case the notifier being an IP-PBX or another Snom phone: Busy state => PFK LED on (colour?), PFK label & icon "on a call"	Must Have
9	BLF-XML-02-05	In case the notifier being an IP-PBX: Hold state => PFK LED blinking slow (colour?), PFK label & icon "on hold"	Must Have
10	BLF-XML-02-06	In case the notifier being an IP-PBX: DND state => PFK LED on (colour?), PFK label & icon "DND on"	Must Have

User interaction and design

User interaction			Requirement reference		Design reference
Monitored extension	Monitoring extension	State	SRV	UA	Figma	Screenshot
does nothing	does nothing	Idle		BLF-XML-UA-02-02	Figma requirement (702 "idle")
lifts up the receiver	does nothing	Busy

Questions

Below is a list of questions to be addressed as a result of this requirements document:

Question	Outcome
(e.g. How we make users more aware of this feature?)	Communicate the decision reached

Not Doing

List the features discussed which are out of scope or might be revisited in a later release.