Shared Line Appearance (SLA)

Legacy PBXes often had a feature called Shared Line Appearance for incoming calls. The functionality basically allowed multiple phones to have a line key tied to an extension or DID and offered several features:

  • Incoming calls would ring all configured phones simultaneously
  • When a phone answered the call, the status light would turn green; on the other phones, the status light would turn red
  • If the caller is placed on hold, all phones’ (answering or not) status lights will blink red
  • Any phone with SLA can pickup the on-hold call
  • When the call completes, all status lights turn off.

Simulating SLA

Simulating most of SLA on a Kazoo system is possible. Let’s take a look at how this might be achieved.

Incoming calls ring all devices

This is pretty straight-forward. In Kazoo, one of the callflow actions is a ring group. Put any endpoints (devices, users, or groups) into the ring group and all calls to the callflow will ring the endpoints according to the strategy provided.

Status lights

Kazoo allow updating a pre-defined presence_id to with BLF updates. You can set this presence_id on the device or user documents, or you can use the manual_presence callflow action to toggle this. Configure the phones’ BLF light to subscribe for this presence_id value to have it update during calls.

Placing on hold for others

The closest way to put a call on hold so others could pick it up is using call parking. Rather than using the hold button on the phone, the answering device can transfer the caller to a parking slot. Once parked, any device that knows the slot number can pick up the call.

Example SLA simulation

Consider the typical executive with an administrative assistant. The assistant’s phone has a line key that will ring when the executive is called. The easiest way to do this is create two devices in Kazoo and assign them to the executive’s Kazoo user.

Create the assistant

  1. Create the assitant’s device 
    curl -X PUT \
    -H "X-Auth-Token: $AUTH_TOKEN" \
    -d '{"data":{"name":"Assistant Device", "sip":{"username":"assistant", "password":"to_the_stars"}}}' \
    http://{SERVER}:8000/v2/accounts/$ACCOUNT_ID/devices

    {
    "data":{
        "id":"{ASSISTANT_DEVICE_ID}"
        ,...
    }
    ,...
}

Create the executive

  1. Create a user for the executive. Be sure to include presence_id="EXT" in the user object - this is what BLF lights will be tied to when setting up presence. 
    curl -X PUT \
    -H "X-Auth-Token: {AUTH_TOKEN}" \
    -d '{"data":{"first_name":"Exec", "last_name":"Utive", "presence_id":"1000"}}'
http://{SERVER}:8000/v2/accounts/{ACCOUNT_ID}/users

    {
    "data":{
        "id":"{EXECUTIVE_USER_ID}"
        ,...
    }
    ,...
}
  2. Create a device for the executive. 
    curl -X PUT \
    -H "X-Auth-Token: $AUTH_TOKEN" \
    -d '{"data":{"name":"Executive Device", "owner_id":"{EXECUTIVE_USER_ID}", "sip":{"username":"executive", "password":"high_roller"}}}' \
    http://{SERVER}:8000/v2/accounts/$ACCOUNT_ID/devices

    {
    "data":{
        "id":"{EXECUTIVE_DEVICE_ID}"
        ,...
    }
    ,...
}
  3. Create the callflow using the ring group action to ring both the executive’s and assistant’s phones. This will also cause a BLF update to presence_id@account.realm to update the assistant’s BLF key. 
    curl -X PUT \
    -H "X-Auth-Token: $AUTH_TOKEN" \
    -d '{"data":{"numbers":["1000"], "flow":{"module":"ring_group","data":{"endpoints":[{"id":"{EXECUTIVE_USER_ID}", "endpoint_type":"user"}, {"id":"{ASSISTANT_DEVICE_ID}", "endpoint_type":"device"}]}}}}' \
     http://{SERVER}:8000/v2/accounts/$ACCOUNT_ID/callflows

    {
    "data":{
        "id":"{EXECUTIVE_CALLFLOW_ID}"
        ,...
    }
}

Now calls to extension 1000 should ring both the executive and the assistant devices.

Create the call park/pickup callflow

Create a callflow, *4{presence_id}, that will have the park callflow action. This will be used by the BLF key to simulate the hold/pickup of SLA. You should set the action to auto and the slot to presence_id. ```shell curl -X PUT
-H “X-Auth-Token: $AUTH_TOKEN”
-d ’{“data”:{“patterns”:[“*4(\d+)”], “flow”:{“module”:“park”,“data”:{“action”:“auto”}}}}’
http://{SERVER}:8000/v2/accounts/$ACCOUNT_ID/callflows

```json
{
    "data":{
        "id":"{PARK_CALLFLOW_ID}"
        ,...
    }
}

auto will retrieve a call if one is parked or park the call if the slot is empty.

Create the BLF key

Create a BLF key configuration on the assistant’s phone to:

a. The “value” (or equivalent) will be presence_id b. The “extension” (or equivalent) will be *4{presence_id}

This will light up with the corresponding call.

When the assistant puts the call on hold, the BLF can be used to pickup the call.

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