Non-Matrix Operation

The Telos Infinity intercom system is a powerful platform because:

• It connects audio and control over IP

• It uses structured cabling and standard IT systems

• It is fully distributed

• It does not use any kind of central mixing or routing matrix

Before Central Matrix Mixing

In the early days of broadcasting, traditional intercom systems were hard wired. Each Panel received every microphone feed of every Panel in the system. An intercom with just thirty Panels would require each Panel to have twenty-nine audio circuits into it. And a central distribution and amplification system would be required to impedance match and distribute each Panel microphone to all the Panels in the system.

Cabling for such a system was complex and flexibility was difficult to achieve. Attaching an extra Panel would require every Panel communicating with it to forfeit one of their existing audio circuits and Panel switcher or add an additional circuit and switch to the Panel.

Adding IFB’s (Interruptible Foldback) and clean feeds was equally difficult as the Panels that could receive or control these circuits was fixed in installation.

This system worked in the early days of television but was rigid and difficult, and making changes was often a prolonged and challenging task.

Central Matrix Mixing

The next development was to use a centralized audio matrix as this improved flexibility but was costlier and more complex. Each Panel had one audio circuit in, for the loudspeaker and headphones, and one circuit out, from the microphone. But a control circuit had to be added so that the central matrix could route the appropriate microphone to the Panel.

The matrix provided one-to-one, many-to-one, and one-to-many mapping. The microphone was the input and the loudspeaker and headphones on the Panel were the outputs. Where one microphone was mapped to a single Panel loudspeaker, such as VT talking to Graphics, a simple one-to-one mapping was achieved using an X-Y cross-point. When one microphone was connected to multiple Panel loudspeakers, such as the Directors open-talkback, a one-to-many mapping was provided using X-Y cross-points and audio mixing. The same was true for many-to-one.

IFB’s and clean feeds were much easier to administer and control. As PC’s became more prevalent in broadcasting, specialist programs ran on them and provided the necessary monitoring and control of the matrix. Often achieving complex configurations and control. Even the labels on top of the Panel buttons could be changed to make them assignable. Different configuration files could be stored and recalled making the whole system highly configurable.

But the main issue with this design was the need for a hardware central matrix. Expanding beyond the capabilities of the frame became a challenge as the connections between them didn’t always carry all audio circuits and control giving a natural limit to the installation size. And as the whole system relied on one matrix, there was a significant single point of failure.

Next-Generation Non-Matrix Mixing

Telos Infinity is the next generation of intercom systems. In an IT network built with resilience and redundancy, there are no single points of failure as there is no centralized matrix. If one Panel stops working, then it will not affect the other Panels in the system. It may not be able to receive or send audio, but it will not stop the other Panels from functioning.

As Infinity uses IP to distribute its audio and control data, it takes advantage of some of the interesting aspects of the IP stack of protocols. Multicast is the method by which a Panel continuously transmits its microphone output to the network. When a push-to-talk button is pressed, the associated Panel will receive a message telling it to route the multicast associated with the sending Panel to its own internal mixing engine and present it to the loudspeaker. At the same time, the receiving Panel’s button will signal to the user who is speaking.

As Ethernet is a packet multiplexed delivery method, each Infinity Panel can receive many simultaneous multicast feeds and mix them in its dedicated hardware. For example, a single 1ms AES67 audio stream with control requires approximately 2.5Mbit/s of data. The 1000Mbit/s IP connection to an Infinity Panel allows for multiple channels of simultaneous communication, far more than would ever be practical to listen to by a typical operator.

As there is no centralized mixing matrix, we do not have to worry about diverse power supplies for it. There is always a risk of a fuse blowing or circuit breaker tripping causing a matrix to crash and fail. Rebooting such a system often takes time and it is entirely possible that the configuration file or even the server could be corrupted during an unplanned power outage, further adding to the problems.

The Benefits of Non-Matrix Mixing

Centralized matrices are usually heavy and create a lot of heat. This can be of concern in a remote broadcast truck where every ounce of weight makes a difference. Extra air conditioning is required, further adding to the power and weight requirements.

Using the Telos Infinity system overcomes this as the weight is limited to the individual low power Panels, all running off 12VDC power or PoE, and is evenly distributed throughout the truck. Audio and control data passes over a single 1000-BaseT Ethernet connector to greatly reduce the weight contributed to by the cables.

Scalability is easily achieved using standard IT network infrastructures. As the audio and control data are distributed using IP packets, they can easily pass over other hardware distribution systems supporting IP, such as high-speed fiber connecting multiple LAN (Local Area Network) Ethernet switches together to form WAN’s (Wide Area Networks).

Expanding the system is easy as there is no central intercom routing or mixing matrix so expanding the system is a simple matter of adding new Panels or beltpacks and configuring it with the drag-and-drop software. There is no need to purchase new matrix frame cards or worry about increasing power requirements and associated air conditioning.

Each Panel and beltpack will store its own configuration in non-volatile memory. If a power loss occurs, then each Panel and beltpack will automatically reboot with the latest version of its configuration database. The Dashboard software running on a PC provides the ability to download new configurations and update each Panel and beltpack, but the system can run independently of it.