# Allow Multiple Registrations for One Extension Number

An extension does not have to live on just one device. You can register the same extension number across several SIP endpoints and Cloud Voice App clients at the same time, so a user can answer and place calls from whichever device is convenient. This page shows how to raise the concurrent-registration limits for an extension.

:::note
SIP (Session Initiation Protocol) is the standard that phones and apps use to connect to the phone system. A SIP endpoint is any device that registers with an extension: a desk IP phone, or a softphone (a phone application running on a computer). "Concurrent registrations" is simply the number of these devices allowed to be signed in to one extension at the same time.
:::

## How it works

People who move between locations often want the same number everywhere: a desk phone in the office, a softphone on their laptop, and the Cloud Voice App on their mobile. When you allow more than one registration per extension, an incoming call can ring every registered device at once, and the user handles it from wherever they happen to be.

Each device family has its own limit, which you set independently.

## Set the concurrent registration limits

1. Sign in to the management portal and go to **Extension and Trunk > Extension**, then open the extension you want to change for editing.
2. In the **Extension Information** section, set a limit for each device type according to how the user works.

   :::tip
   Set each limit to match how the person actually works instead of maxing everything out. Fewer registered devices means fewer surprise rings to chase down, and it is easier to troubleshoot when something misbehaves. You can raise a limit later at any time.
   :::

   
   ![Cloud Voice, Extension Information fields for the four concurrent-registration limits](/images/pbx/concurrent-registrations.png)

   | Setting | What it controls |
   | --- | --- |
   | IP Phone Concurrent Registrations | How many SIP phones may be registered to the extension at once. Maximum: 5. This example uses 3. |
   | Cloud Voice App Web Client Concurrent Registrations | How many Cloud Voice App web sessions may be signed in at once. Maximum: 3. This example uses 3. |
   | Cloud Voice App Desktop Client Concurrent Registrations | How many Cloud Voice App desktop clients may be signed in at once. Maximum: 3. This example uses 3. |
   | Cloud Voice App Mobile Client Concurrent Registrations | How many Cloud Voice App mobile clients may be signed in at once. Maximum: 3. This example uses 2. |

   The values in each drop-down are capped at the maximums shown above, so you cannot set a limit higher than the system allows.

3. Click **Save**, then **Apply**.

## Result

With the example values above, the extension can be signed in to 3 web clients, 3 desktop clients, and 2 mobile clients of the Cloud Voice App, and registered on up to 3 SIP phones, all at the same time.

When a call comes in, every signed-in Cloud Voice App client and every registered SIP phone rings according to the extension's [ring strategy](/pbx/administrator-guide/presence-settings/#configure-presence-status__section_dyj_lbj_ymb), and the user can answer from any of them.

:::note
By default, if the extension is already on a call and another call arrives, the other devices still ring. To stop the remaining endpoints from ringing while one is busy, go to **Extension and Trunk > Extension > Features > Call** and enable **All Busy Mode for Endpoints** for that extension.
:::

:::caution
Enabling **All Busy Mode for Endpoints** means a second caller cannot reach any of the user's other devices while one call is in progress. Turn it on only when that behavior is wanted, or the extension may miss the second call.
:::