Turning an IP Camera Into an Intercom

By Brian Rhodes, Published Jul 19, 2012, 08:00pm EDT

Several integrators have recently sent help requests looking for guidelines on using IP cameras as part of a single station intercom system. In this note, we examine one of those requests and provide our answer:

Problem Statement

Here is a request we recieved:

"I am looking for some advice to use an Axis #P3344-VE Camera with a Louroe #AOP-SP-PB (Bi-Directional Door Station). I am trying to get around having to put in a separate Aiphone Door Intercom system. This is simply a connection between the receptionist (her computer) and the back gate to a school. I am missing the software component. I could be wrong but I don't think the Axis software or the Exacq software can do the live audio needed to create a basic door intercom system. Any suggestions? "

For those unfamiliar with the pieces involved, the integrator wants to use an Axis dome camera to host two-way audio from a Louroe intercom station. The desired user must be able to 'hear', 'talk to', and 'see' activity at the back gate via a VMS viewing client or Live View pane.

This question has two major elements to answer:

  • Will the hardware integrate together properly?
  • Will the VMS software support intercom function?

Both elements must work together in order for sufficient operation. In the section below, we address each element:

Problem Solution

Will the hardware integrate together properly?: In the case of the above equipment, the Louroe AOP-SP-BP [link no longer available] is able to be directly connected to DVR, NVR, or IP camera audio inputs. This intercom station contains a separately powered loudspeaker and microphone, providing sufficient listening and speaking volumes at the back gate.

However, in order to support 'two way' communication, the camera must have both 'audio in' and 'audio out' ports available. The Axis camera, a P3344-VE contains both of these jacks.

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The other critical attribute the camera must contain is an I/O port, so that the intercom unit's 'call button' can be used to trigger intercom function. Again, the P3344-VE contains I/O ports.

One aspect not clearly addressed by the question above, but important to consider, is how the 'desired user' will hear voice communication with the intercom. In some cases, it may be possible to hear/speak to the intercom via connected headphones and mics to the viewing workstation. However, this may not always be possible due to workstation, VMS, or other constraints. A local external 'hotspot' speaker/microphone may be required. In this case, Louroe sells another intermediate device, the AOP-XD interface, that permits external listening/speaking devices to be connected to the intercom station.

In the case above, the integrator clarified that no additional equipment was necessary, and that the end-user would be fine using computer workstation connected speaker/microphone. In this case, Louroe furnishes an example wiring diagram depicting how best to install this equipment:

connecting

Notice the primary communication cable requires 3.5mm minijack connectors to be soldered to the 'camera end'. Aside from this, all other connections are made in traditional screw terminal block or punchdown connectors.

Once the hardware is hung, connected, and powered, the camera has to be configured to recognize the audio input/outputs, and the wired connection of the callbutton. In the case of the Axis camera above, simply checking the appropriate 'audio enabled' checkboxes in the 'Setup' tabs permit voice traffic to flow freely.

VMS Support for Intercom

The integration of the call button is a little more complex, where an 'event' rule must be created that, upon call button button push, it enables the audio feature. Typically, sending an alarm triggers some form of notification to the end-user, and begins recording. The exact flow of this operation can be configured in several ways, and is determined by how flexible the camera controlled logic can be configured. Not all cameras are equal in this flexibility.

In the case of this particular request, neither Exacq nor Axis Camera Station support two-way audio functions. In both cases, audio can be 'heard' from the camera and written to storage, however no provision for 'audio out' exists through the VMS interface. Exacq suggested,

"Have them open up the camera web page on alarm, and use that interface for the two way audio. The limitation is that it would not record or only record half the conversation."

This reply demonstrates the importance of checking supported features of a proposed platform. Exacq's response provides a manual 'workaround' solution, which may prove to be sufficient to the end-user, but otherwise precludes 'audio out' recording of events.

With regards to the original request, the suggested workaround solution is accepted. It involves configuring the VMS software to be alerted, by way of camera, when the call button is pushed and to open a 'Live View' webpage of the camera external to the VMS platform. From this point, the camera webserver is configured to open the audio channels so that communication can take place. The operation may conclude with a command to close the 'Live View' webpage after a period of inactivity and revert back to VMS-only camera viewing.

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