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CERNphone desktop User Guide

Below are instructions on how to use CERNphone desktop, for basic and advanced functionality.


Instructions on how to migrate to CERNphone are found here.



Start the app and choose between your common web browser login or the in-app login.

You can log in using your primary account, or using a service account.

Sign in

After successful authorization the personal and/or shared phone numbers that are associated with the login account are displayed. Select the phone number you want to work with.

Select phone number

The CERNphonephone app is then launched and registered with the number you selected, you are ready to make and receive calls.

CERNphone desktop app


Every instance of the application can have only one phone number active at a time. Only one CERNphone app can run at a time on a desktop.

Connection status mode (Available / Silent mode / Do not disturb)

There are 3 connection status modes that you can activate/deactivate by clicking on the current status indicator:


  • Available

  • Silent mode : incoming calls will not generate any ringtone on this device

  • Do not disturb : calls are redirected to voicemail (if activated) or rejected, on all your devices.

Pop-up notifications for incoming and missed calls

To enable pop-up notifications for incoming and missed calls:

on Mac: Open the System Preferences app and click on the Notifications icon. Navigate on the list to the left to CERNphone Desktop and activate Allow Notifications from CERNphone deskop. We recommend to set the alert style to Alerts, to enable Show notifications on lock screen, and to set Show notification preview to always, so that you can see notifications even on the lock screen:

Mac notifications preferences

on Windows: go to Focus assist in the Settingsof your computer and select OFF:

Focus assist

Sound devices and ringtone

To change the input/output devices, select your preferred devices from the drop down list in Settings Settings -> Devices. You can then test the ringing and output devices. If you have problems with your audio devices, please check also the following detailed procedure in SNOW.


Changing the default ring tone: In the Change ringtone sound section, you can also use your own ringtone by using a .WAV format audio file.

Compact mode

To use the app in a "Compact mode", reduce manually the main window of the application, or go to the menu bar -> Window -> Toggle Compact mode:

Compact mode


The CERNphone desktop app saves operational data to a log file. These logs may be requested by the support team to debug an issue with your client. To easily access this log file, open the App menu, then click Open logs folder. The log file is simply named log or log.log.

Basic functionality

Issuing a call

To make a call search a person by name in the search field. Click on the name of the person and select the number to call.

Search contact

Alternatively, use the Dialpad to enter the number and call it. To call a CERN fixed or mobile number, enter the complete number (+41 22 767/6 xxxx, +41 75 411 xxxx) or use the short numbering (7xxxx/6xxxx/16xxxx).


You can also click on the name of the person in Contacts Contacts or in Recent calls Recent calls.

During a call, you have the following options:

in call options

From left to right:

  • Mute the microphone

  • Put the call on hold (the remote party will hear Les Horribles Cernettes as music-on-hold)

  • Hang up the call

  • Open up the DTMF dial pad (see below)

  • Add a new call or transfer the ongoing call (see below)

Managing concurrent (parallel) calls and multi-person calls

CERNphone supports multiple concurrent calls:

  • Starting a new call when in a call: Click on the + icon below the number, select the new contact or number you want to call (by selecting one of your contacts, searching the address book, going into history, or dialling the number). You will be given the choice to start a new call:

Start new call

  • You can then change amongst the participants by clicking on the corresponding number in the top row, which then will be highlighted. You can have up to 4 concurrent calls. Only one call is active at a time, the other participants will hear music-on-hold.
  • You can also merge all calls into a single one (and to separate them again) by clicking on the blue icon to the top right. Note that if you hang up a merged call, the call terminates for all participants. See also below for setting up a three-party conference.

Concurrent calls

Issuing a call to external numbers

To call an external number, two options are available:

  • Call the external number directly if you have specific access rights on your landline. You can check your call rights on ERT, column Access Rights, with the following possible values:

    • CERN numbers only: CERN fixed and mobile numbers; but with CERNphone, local area calls are also authorised.
    • Local: In addition to CERN numbers, also numbers in the local area (prefixes +33450, +4122, +4121). For all CERNphone numbers, this access right is granted by default.
    • Worldwide: International call rights.
    • To obtain Worldwide call rights please complete this EDH request form in agreement with your management. Select Fixed telephone line modification and provide your number. Please note that external calls must be of strictly professional nature.
  • Call the external number via the Automatic Switchboard System : 79999.

    • Dial 79999 and follow the instructions. Your call will be transferred providing you have a valid budget code associated to your CERN ID. This number is available for users occasionally calling outside CERN for professional or personal purposes.
    • When dialling the destination number, please use 00 instead of + for the international prefix (e.g. 0049XXX.. instead of +49XXX..).
    • Paid members of the personnel holding a contract of three months or more can also use the 79999 to make occasional private calls (the expenses can be deducted from their monthly salary).
    • The use of this service is governed by the Operational Circular Nº5 (OC5).

External number formats:

  • For Switzerland: Enter the number with or without Swiss international prefix (e.g. 079 xxx xxxx or +41 79 xxx xxxx).

  • For all other countries: Enter the complete number with the international prefix (e.g. +33 6 xxxx xxxx)

  • When using the 79999 Automatic Switchboard System, please use 00 instead of + for dialling the destination number in international format.

Use of DTMF tones (Voice Frequency) for menu navigation (press 1,2...)

The dialpad of CERNphone desktop generates DTMF signals.

While in a call, click the Display DTMF button Display DTMF.

DTMF signals are traditionally used by automated telephony services to take your input (“Press 1 to be connected to the support service” or “dial your meeting number followed by the # key”).

You can also instruct to send these commands when dialling, by using the comma (,) sign as a pause separator. Example: typing +412345,1234,5678# in the dialler field will call the number +412345, then pause, then send 1234 as DTMF commands, pause again, then send 5678#.

Add names to the contact list

For contacts in the CERN phonebook: Search a person in the search field. Click on the name of the person and click on the star symbol next to the name. The new contact will appear at the left pane.

Add to Contacts

For other contacts: You can also enter your own contacts (e.g. those not in the CERN phonebook) by selecting the Contacts tab, scrolling to the bottom, and clicking on + Add Personal Contact.

Launching calls from a web browser or from a local address book

Launching a call from a web browser: On Windows and Mac (and soon on Linux), CERNphone desktop registers several handlers for telephony URI's (tel:, cernphone:, callto:). For example, clicking on tel:11111 launches a call to the echo test number 11111.

  • Note that on some browsers, after clicking on the number for the first time, you may first have to chose CERNphone as the application to use for calls. In the case of Firefox, double-click on "pick an app" in the corresponding pop-up window.

Launching a call from the macOS Contacts app: You can set CERNphone as default application for placing calls when clicking on entries in the MacOS Contacts app. For this, open the FaceTime app, open Preferences under the Facetime menu, scroll down and set CERNphone desktop as Default for calls:

Facetime settings

Launching a call from the command line: CERNphone desktop can also be invoked from the command line with a number passed as parameter. This can be useful for custom address book integrations. For example, for calling 11111 you can run

  • Linux: ~/Applications/cern-phone-app.AppImage tel://11111 (replace the path with the location of the app)
  • Windows: "%UserProfile%\AppData\Local\Programs\cern-phone-app\CERNphone desktop.exe" tel://11111
  • Mac: open tel://11111 (or alternatively, /usr/bin/open tel://11111)
Availability status (in a call)

On the Contacts tab, a red icon will appear for all your CERNphone contacts that are currently in a call. (It will be soon possible to see which of your contacts have Do Not Disturb enabled, and later also which ones are busy according to their Exchange calendar).

Integration with Mattermost for chats and calls

Opening a Mattermost chat with someone

You can open a Mattermost chat with another person by either going to the Contacts tab and clicking on a contact, or by searching for someone in the main tab. When clicking on the contact, you will see a field to open Mattermost:

Mattermost message

By clicking on the Preferences tab, you can select whether you want to open Mattermost in a web browser or use the Mattermost app.

Calling someone from within Mattermost

From within a Mattermost chat, click on the icon of the person you want to call. This will open up the user pop-up. Clicking on the CERNphone link will open your CERNphone app and start a call to the user.

Mattermost call

Advanced functionality

Call transfers and 3-party conferences

To transfer an ongoing call, click on Plus.

Call transfer step1

Select a contact to call from the Search tab or from the Recent call list or directly input the phone number and press Call button.

Call transfer step2

The following call transfer options will be available:

  • Hang up and call -> chose this option if you want to end the current call and initiate a new call.

  • Add new call -> chose this option for starting a new concurrent call (see FAQ above).

  • Blind (immediate) transfer -> chose this option if you want to transfer the call immediately, without speaking to the called person first. Once the call is accepted, it will be dropped on your end. Please note that you need appropriate external call rights for transferring calls to external numbers. Also, blind transfers from external to external numbers, and from CERN mobile to external numbers, are generally not authorised. For this, you need to perform an attended transfer.

  • Attended transfer -> chose this option if you want to speak with the called person before the call is transferred.

Call transfer step3

During an attended transfer, you will be first put to talk with the person to which the call is to be transferred (the transferee), and the caller is put on hold. If the destination person accepts the call, hang up and the call will be transferred. If the destination doesn't accept the call, they should hang up and you will be put back in conversation with the caller. Please note that you need appropriate external call rights for transferring calls to external numbers.

The following additional options are available:

Attended transfer options

From left to right:

  • Abort the attended transfer

  • Initiate a three-way conference with the caller, the transferee and yourself. Contrary to the multi-person calls, you can leave the conference at any time, without the call to be terminated for the other two participants.

  • Swap between the caller and the transferee (the other party will be put on hold)

Other advanced features (call forwarding, Do Not Disturb, team call groups)

To configure call settings such as call forwarding, simultaneous ringing, voicemail or missed call notifications, as well as team calls, go to the CERNphone User Portal. You can also access the CERNphone User Portal by clicking on Settings Settings and selecting Go to CERNphone User Portal (see below). For knowing more about the CERNphone User Portal settings, please consult the following documentation.



White screen instead of login screen (whith Microsoft Edge)

If you're trying to login using your default browser (instead of logging in within the app) beware there's a known issue with Microsoft Edge. We've seen that in some cases the browser opens a window but instead of showing CERN's login screen or redirecting back to the application right away, it shows a blanck screen and doesn't show the login page. In this case, please check Edge's Internet security settings, if it's set to "Strict" that may be the root cause. In this case you may lower the security settings in general or add a exception for whitelisting both cern's and cernphone's login page, and respectively.