Welcome!

This manual provides a comprehensive overview of the CTI API and its functions. The CTI API is continuously being developed to meet the changing requirements and expectations of our customers. 

Please send an email to integration@nfon.com to stay up to date with developments and any changes.

Subject to change
Version 2 / 08/2025 (EN)

Used symbols

The CTI API extends the NFON telephone system service with a powerful interface to support CTI (Computer Telephony Integration) activities.

The CTI API enables seamless and customised integration of cloud telephony with comprehensive CTI convenience features. This leads to a significant improvement in communication and collaboration within the company and beyond.

This manual also supplements the documentation of the OpenAPI specification.

The CTI API is designed as a server-to-server API and enables access to information in the context of a telephone system (see also Access and security).

The API credentials can be requested at vertrieb@nfon.com or auftragsbearbeitung@dt-standard.de. The email must contain the following information:

• K account

• Approximate number of extensions

• Completed declaration of consent (find the template here)

• Email address of the partner to whom access data is to be sent

• Email address of the customer representative

The CTI API is an API designed for server/server communication. It is compatible with any device, e.g. hardphone, softphone or a mobile app. The supported features include call control, call event streams and device management.

The CTI API has been developed to enable the creation of customised integration solutions based on the API. This includes the integration of third-party applications with the following features, for example:

• Contact pop-up
  When an incoming call is received, a CRM system is opened based on the incoming call number. Depending on the customer requirements, the contact window can be opened when the phone rings, after the call has been answered or by an action (e.g. hotkey).

• Contact preview
  When a call comes in, a pop-up appears with the name associated with the phone number, which is retrieved from a CRM system. This information can be enriched with further information from the CRM system, such as the number of open tickets.

• Synchronising line status
  To display employee availability transparently, the line status can be read out and displayed in a customised overview. The NFON Line Status can also be enriched with information from other communication applications (MS Teams, Slack) or calendars (MS Office, Google Calendar).

• Start/end call
  With CTI API, it is possible to start or end calls directly. This enables calls to be started and ended via CRM systems.

The following use cases are also possible:

• Action URL
  Based on the CTI API, Action URL can be developed for incoming calls, answered calls and ended calls.

• Customised ringtones
  The API can be used to use dedicated ringtones for internal, external or VIP calls. In this case, it is advisable to mute Cloudya or the corresponding device.

• Call analytics
  If the streamed events (see 2.2.5 Stream call details) are saved, it is possible to read important information from them. However, please note that the status of individual extensions is not transmitted when the API is initially connected.

The most important functions are listed below. For further details, refer to the OpenAPI specification.

1. Read out extension configuration ‘Get /extension/phone/data’
   This endpoint provides an overview of all configured extensions on a K account, including both the number and the name assigned to the extension.

2. Read out line status ‘Get /extensions/phone/states’
   This endpoint allows you to read out the line status for each extension. This allows the respective availability status for each extension to be displayed in third-party applications. When connecting for the first time, the status of all configured extensions is displayed.

3. Start call ‘Post /extensions/phone/calls’
   This endpoint initiates a call for an extension. First, the call is made to the A

   number and, after acceptance, the call is established to the B number. The user can individually specify which end device rings for the user of the A number. A UUID is transmitted as the return code for this endpoint, which can be used to end calls.

4. End call ‘Delete /extensions/phone/calls/{uuid}’
   Ends a call initiated via the API using the returned UUID.

5. Stream call details ‘Get /extensions/phone/calls’
   This endpoint enables the streaming of all incoming and outgoing telephone events of a K account in real time. For complex environments, it is necessary to take into account the restrictions indicated above. Unlike the endpoint for reading the line status (see above 2. Read out line status), the current status of all extensions is not displayed when connecting for the first time.

The CTI API can be used to add customised CTI features to the client.

The CTI server has direct access to the above-mentioned endpoints in the NFON data centre and can execute Get and Post commands there. If a third-party client is still in use, the CTI server acts as an intermediary between this client and the NFON data centre. Once the CTI server accesses the data in the context of a telephone system, access to the data for the respective client must be ensured in the CTI server.

Security and data protection play a crucial role when using the CTI API. The data provided is sensitive telecommunications data that must be managed with appropriate professionalism.

The CTI API enables access to all data in the context of the K account. The user of the API is responsible for ensuring that each user only receives the data for which they are authorised.

Regular security updates ensure that all technical components fulfil the current security requirements. Users of the CTI API are also responsible for taking appropriate security precautions when using the data.