AXIS 2191 Audio Module

Add the ability to hear and speak through an Axis network camera unit and explore new video communication possibilities over the Internet and other networks.

Simply connect the AXIS 2191 Audio Module to an Axis network camera or video server, and you'll have access to real-time images, as well as two-way audio communication from an Internet Explorer Web browser.

System overview

When an Axis network camera is connected with an AXIS 2191 Audio Module, the combined unit enables many people at different locations to access the same images and sound at any one time. 

Easy to install

There's no need to connect a PC to the network camera/audio unit.  The audio module connects easily to the serial port of the network camera. The module is equipped with a built-in microphone; alternatively you can connect an external microphone. The module is compatible with most microphones and loudspeakers/headphones. Note that the network camera/video server must have the correct firmware version installed.

Easy to use

There's no need to install cumbersome client software. To access sound and images from the network camera/audio unit or speak through the unit, all you need is to open an Internet Explorer Web browser with a computer that is equipped with a soundcard, microphone and loudspeakers. The network camera's user interface provides all the tools required for managing the audio module. Four audio modes are available, for details - click here.

How does it work?

At your company entrance, a doorcam system (consisting of an AXIS 2191 Audio Module and an Axis network camera) is mounted on the wall. The opening mechanism for the door is controlled by the output port of the network camera.


1. A visitor arrives at the front door and presses the doorbell to ask if he can come in.

2. With your Internet Explorer Web browser opened to the doorcam's Home Page, you can see the visitor and hear his request.

3. Using a microphone on your PC, you send a voice reply back to the visitor, and with a simple click of the mouse, you open the door to let him in.

Questions & answers

Q: Which Axis video products does the AXIS 2191 Audio Module support?
A: The audio module is compatible with the AXIS 2100, 2110, 2120 and 2420 Network Cameras and the AXIS 2400/2401 Video Servers.

Q: How do I connect the AXIS 2191 Audio Module to the network?
A: The audio module cannot be connected to the network. You simply connect it to the Axis network camera's serial port via a null-modem cable. The sound is compressed in the module and sent to the camera which then redistributes it to the PC client using its in-built Web server.

Q: Which extra software does the client PC need?
A: The PC client only needs Microsoft Internet Explorer 4.0 and higher. The Axis Active X control will be installed on first use.

Q: Which hardware does the client PC need?
A: It depends on the application. However, to take full advantage of the audio module's functionality, we recommend a PC equipped with a full duplex sound card and good quality speakers and microphone, alternatively a headset.

Q: Does the audio module have in-built speakers?
A: No, an internal omni-directional microphone is available – for optimal performance. We recommend a uni-directional microphone and good quality speakers.

Q: Can I use the audio solution over modem?
A: No, the audio module occupies the serial port of the network camera. Besides, the bandwidth would be to low.

Q: I want to monitor my branch offices using video and audio. Which bandwidth do you think I will need?
A: The audio occupies 39,2 kbit/sec of bandwidth in simplex mode (71,2 kbit/sec in duplex). This is added to the the data stream of the video which is depending on the frame rate and resolution you choose. An average picture of 12KB with a resolution of 352 x 288 at 1 frame/sec occupies 96 kbit/sec of bandwidth. Adding some network overhead will give 192 kbit/sec as a realistic recommendation.

Q: Can I use the audio module for video conferencing with remote sites and SOHO workers?
A: Yes, it’s possible - although not a focus application. Keep in mind that the high quality images of Axis network cameras can have a severe impact on low-bandwidth links. If you need two-way video communication, a video conferencing system using H.323 would is a better choice.

Q: Can I record the audio?
A: No, recording solutions for audio are currently not available.

Q: How are pictures and audio sent? Are you using MPEG?
A: The pictures are sent using motion JPEG over HTTP. The audio is sent as a separate stream of digital audio (ADPCM G.721) using the same protocol.

Q: How is audio synchronized with the motion JPEG stream?
A: The audio and video are not synchronized which has little impact in practical use as the audio are prioritized ahead of the video stream – the basic concept is that the audio should come through at all times even if the available bandwidth might cause the images to be updated more slowly.

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