Customers that use cloud PBX can supervise their colleagues’ calls in real time. For example, a manager can listen in on a sales agent’s calls, guide them, and, if needed, participate in the calls.

Call supervision is available in three modes:

  • Spy mode – a manager can join an active call to listen in on the agent and the client's conversation without revealing the manager’s presence. For example, managers can silently monitor calls to provide feedback afterward and suggest improvements to agents’ communication skills.
  • Whisper mode – a manager can speak to the agent directly while the client is not hearing the manager. The manager can assist the agent and give tips during the conversation with the client. For example, managers can use this mode when training new agents.
  • Barge-in mode – a manager can speak to both parties – the agent and the client. For example, the agent has trouble handling the client’s concern, so the agent asks the manager for assistance. The manager joins the call using the barge-in mode to speak to the client directly.

A manager can choose any of these modes when joining an active call and switch between modes during the call.

  • PBX customers can use call supervision to train new agents, evaluate their performance, and improve customer service, sales, technical support, etc.
  • Managers can ensure that agents process calls in a way that meets the company’s standards.
  • Agents receive help from the managers in real time and can resolve issues on the spot.

Let’s consider an example.

The ABC company has a call center with customer support and sales teams. Adam is a manager of the customer support team. He is authorized to join agents’ calls to assist or provide feedback. John is a new agent in the customer support team with the extension 744.

Adam sees on the special IP phone console that John has an active call with a client. Adam decides to check how John is handling the call. To join the call in spy mode, Adam dials *90744 (where *90 is the Spy mode prefix and 744 is John’s extension). Now Adam can hear the conversation.

John answers a few of the client’s questions. When the client asks another question, John can’t find the required information. John requests assistance from Adam in the corporate chat. Adam has already been listening in on this call, so he switches to the Whisper mode by dialing 1. Adam tells John how to find the information.

The client keeps asking about the service details. Adam decides that John needs help in handling this call. Adam switches to the Barge-in mode by dialing 2, introduces himself to the client, and explains the relevant details. The client is satisfied with the provided information, and the call ends.


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To configure call supervision, these steps must be performed:

  1. On the PortaBilling administrator web interface. The administrator enables the call supervision feature for the customer: opens the Customer record > Services > Voice calls > turns on the Call supervision toggle > Save.The administrator enables the call supervision feature
  2. On the customer web self-care interface. The customer configures the extensions in a hunt group that are authorized to access the other hunt group members’ calls.

For example, to add Adam as a manager of the  "Support" hunt group, the customer opens the Cloud PBX tab > Hunt groups > "Support" hunt group configuration > Add extension > fills in details > selects the check box for Supervision allowed option > Save.

The customer enables the Supervision allowed option for the extension

An extension authorized to access the other huntgroup members’ calls

Switching the modes using service codes

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The default prefixes and Dual-Tone Multi-Frequency (DTMF) codes for call supervision feature:

Call supervision mode

Prefix to join an active call

DTMF code to switch to this mode from any other

Spy mode



Whisper mode



Barge-in mode



For example, to join a call made by an agent with extension 888 in the whisper mode, a manager dials the corresponding prefix followed by the extension: *91888. To switch, e.g., from the whisper mode to spy mode, the manager dials the DTMF for the spy mode: 0. To switch to the barge-in mode, the manager dials 2.

How to change the service codes for call supervision

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You may need to change the default service codes for the call supervision feature.

Example 1

IP phones of some models, e.g., Linksys SPA-942/SPA 941, may already have default service codes like *90 that coincide with the PortaSwitch service codes for call supervision (*90, *91, *92). So, to enable call supervision from such phones, you need to set different service codes in PortaSwitch.

Example 2

A customer migrates to cloud PBX from their legacy PBX. The customer’s managers are used to the call supervision prefixes *21, *22, *23, and DTMF codes 1, 2, 3 which are different from the default service codes in PortaSwitch. The customer wants to keep their old service codes. To change the default service codes (prefixes and DTMF codes):

  • creates a customer record with the dialing rules option enabled;
  • creates a new dialing rule of PBX type; and
  • changes the default prefixes and DTMF codes in the dialing rule.

The administrator creates a new dialing rule of PBX type

Customers can edit the supervision prefixes and DTMF codes on their customer self-care interface: they need to open the Cloud PBX page > Dialing rules, switch to the Custom rule, and change the call supervision prefixes and DTMF codes.

The customer switches to the Custom rule

Call supervision from external apps

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You can enable the PBX customers to supervise calls using third-party or in-house developed applications such as CRM. The manager can see the list of calls in progress when they open their CRM page and can join an ongoing call by pressing a single button. In the background, the CRM widget sends a call control API request to PortaSwitch which initiates a call to the manager’s phone. As soon as they pick it up, they automatically join the active call. Once the manager is on the call, they can switch between the Spy, Whisper, or Barge-in modes in one click and monitor or assist their employees.

The application uses the new CallControl/join_to_active_call and extended CallControl/update_on_spot_conference_participant methods to enable call supervision.

  1. To enable using the call supervision feature, make sure that the role of the customer/account allows call control (check Role > Permissions > Other features > Call control – Modify).
  2. A manager under the customer realm can add any account as a supervisor to the call initiated via their application with no need to additionally enable the call supervision feature for this account. However, if the account (under the account realm) initiates the call supervision, the Supervision allowed option should be enabled.
  3. Switching the modes using service (DTMF) codes is unavailable in the calls initiated via the application for now.

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