What were once just simple point-to-point voice communications devices have grown over the last two decades into major communications networks and large installations. This evolution of intercom systems also brought about a change in perspective. While it used to be good enough to just provide a simple communications link between two or more users, nowadays, several different data and signal types need to be integrated into an overall network. Furthermore, installations are getting increasingly complex, demanding new approaches and new solutions that do not only include communications within one production site, but also link together multiple production locations simultaneously.
What are the requirements for modern intercom systems? What solutions are already available, and what ideas should be further expanded? This article gives a brief overview of the current trends in intercom design and offers an outlook on possible future developments and ideas.
Requirements for modern systems
The demands on contemporary intercom systems are as diverse as the installations where they are used. Sometimes large production facilities with hundreds of users need to be equipped, and other times, it's just a couple of control panels at a theater production.
To provide a solution for all of these different applications, a modern communications infrastructure needs to be scalable from small, single-matrix systems up to very large, networked intercom systems with more than 1000 ports. In this way, the same technology platform can be easily used in large studio facilities, as well as in small trucks or event installations. Without such a high level of scalability, the planning, installation and maintenance of any system would require more work than necessary and would not be cost-effective. However, with scalable systems, established solutions can be easily adapted to new environments, securing prior investments.
As much as scalability is important, modern intercom systems also need to be able to handle a large number of different signal formats. Today's intercom systems are doing more than just providing a communications link between two people; analog and digital audio signals, IP data, control data and GPI signals are all interfaced in contemporary digital intercom applications. How an intercom system handles different signal types and integrates them is an extremely accurate indicator of its usability. The seamless integration of four-wire analog, AES3, MADI, Ethernet, VoIP and GPIs should be a given in today's systems.
Reflecting the importance of intercoms in today's production processes, reliability remains an important issue for intercom installations. For example, redundancy provides maximum reliability in modern intercom systems. Hot-swappable components, redundant CPU and PSU units plus redundant network topologies have proven to be the most successful solutions in protecting installations against failures and dropouts.
One aspect that is often neglected is the usability of the intercom system itself. The way it is configured, operated and maintained plays a major role in determining how well it will perform in day-to-day field operations. Shorter production cycles require greater system configuration flexibility and the option for a higher degree of automation. Optional control via external router control systems is also a feature that increases the degree of studio technology integration.
Different network approaches
To understand modern intercom systems, it's important to comprehend their different technological approaches. In intercom system architecture, four main paradigms are apparent in current thinking:
- Star topologyIn star topologies, all control panels are connected to one central mainframe. Although this makes planning the system quite easy, the effort of setting up larger systems is extremely high, especially regarding cabling. (See Figure 1 on page 8.)
- Bus networkBus, or trunk, networks are similar to star topologies. The network consists of several star topologies with nodes that are connected, or trunked, together. Additional four-wire cabling expands the bandwidth between the various mainframes. (See Figure 2 on page 8.)
- Meshed systemIn meshed systems, all mainframes are interconnected with one another. This ensures the continuous operation of the complete installation if one node stops working. With larger systems, the cabling requirements grow exponentially, and this topology is the most demanding in terms of cabling and setup. (See Figure 3.)
- Ring topologyIn a ring topology, all available mainframes are connected in a dual fiber ring. Even in large systems, the effort needed for cabling is reduced to a minimum. (See Figure 4.)
Each of these four approaches is different in terms of performance and reliability. Ring topologies and meshed systems are able to handle a high amount of bandwidth. In particular, ring topologies, with their non-blocking network approach, are able to provide maximum network and communications performance. Star topologies and bus/trunked systems, on the other hand, suffer from significant bottleneck issues. Especially when there are a high number of calls or significant data transmission, the whole system will be throttled down or calls will not make it through due to a lack of bandwidth. Therefore, it is not recommended to rely on systems based on a star topology when reliable performance is always needed.
In regards to operational reliability, both the star topology and bus network systems are prone to single points of failure. The failure of one node within a trunked system, or even just a connection failure between two nodes, can bring the whole system down. Redundant ring topologies and meshed systems are secured against these kinds of problems. Because there is no master mainframe and every link is set up redundantly, the entire infrastructure will stay online even if a node or a link stops working.
Cabling is another important aspect when it comes to intercom system infrastructure design. Fiber has been proven to be the most flexible and cost-effective solution to link matrices within a facility or a city. With its high bandwidth, fiber enables the transport of large amounts of data over long distances. Yet, the most efficient way to realize the connections between a mainframe and control panels is over copper-based Cat 5 or coaxial connections. This solution allows adequate cable length while still keeping the material price down. Connecting the matrix to the panel digitally via a standard AES3 signal, which transports the panel control data within the signal's bits, provides further advantages.
Applications in today's field operations
Beyond topology and network concerns, connectivity is one of the most important considerations for an intercom installation. This can be thought of in two different ways: One aspect is the kind of signals that can be integrated, and the other is how the intercom system transmits the integrated signals and the kind of transmission protocol used.
Three considerations should be taken into account regarding signal integration. First, modern intercom installations deal with much more than just speech transmission. Second, this requires a greater variety of signal formats. Third, this means that a higher signal density needs to be handled by the network. It is, therefore, no surprise that all of these new signals are based in the digital domain. The way an intercom handles digital signals, and especially the combination of analog plus digital signals, is a good indicator of its usability and the degree to which it is prepared for future applications.
The most common digital signals used are AES3 for common audio transmission and MADI for multi-channel audio transmission. In the design of current intercom installations, these formats need to be transported efficiently within the intercom installation. Interfacing to AES and MADI allows system designers to integrate digital audio routers seamlessly with the intercom system. (See Figure 5.)
Incorporating these signals into the matrix offers several advantages. For instance, managing all communications with digital audio in real time allows the easy integration of broadcast-quality commentator audio at the panel or the feeding of multiple IFB sources to the matrix. This minimizes the installation requirements and reduces costs significantly. It adds flexibility, especially when it comes to integrating other equipment into the infrastructure. Relying on nonproprietary, standard-conform data types like AES3 and MADI also helps keep the installation flexible.
Another crucial factor for modern intercom systems is the way that signals are handled within the network itself and in combination with the outside communications world, including remote installations. Merged time-division multiplexing (TDM)/IP solutions that combine real-time TDM-based and IP-based communications into one integrated network are the answer to this demand and a standard solution provided by all intercom manufacturers. On the one hand, there is on-site communication, which needs to be handled in real time for obvious reasons, such as the general need to avoid latency and the use of commentator audio. On the other hand, networking over greater distances is best handled via IP signals because it's the most cost-effective way.
Connection in real time is not a priority in these cases — for example, when connecting to distant studios. It's apparent that former long-distance communications solutions such as ISDN and analog hybrids are going to be replaced by completely digital IP-based solutions. For this reason, any modern intercom should be able to work with both approaches at the same time. Relying on only one approach would extremely limit the possibilities of the given installation.
Current intercom systems rely to a large extent on hardware components such as matrices with processor and client cards, control panels and interfaces to provide all the functionality needed. (See Figure 6 on page 12.) To expand the flexibility of future systems, intercom infrastructures will need to incorporate software-based functionality. This will ultimately result in hardware components only providing the basic infrastructure, upon which the software-based intercom features will run. In the long term, the feature set of the software of an intercom platform will become more important.
Following this development, it is apparent that the usability of those software features will play a major role in the success of a specific intercom system. Features such as easily configurable IFB tables, extensive audio routing capabilities, GPI integration or real-time system monitoring, and remote control are indispensable for contemporary intercom applications. (See Figure 7.)
Given that modern communication systems are usually a lot more than just a matrix intercom installation — consisting of, ideally, digital partyline intercom components, wireless intercom solutions and professional mobile radios — it's obvious that contemporary solutions need to integrate all of these communications types into one single digital infrastructure, which can be administrated via one integrated control surface.
This integration is the only way that modern intercom systems based on standard components can be adapted specifically to the individual needs of every installation without costly adaptations and special developments for each project. Any intercom can only be as effective as it is reliable and flexible in terms of connectivity, data types and network architecture.
Andreas Hilmer is director of marketing and communications at Riedel.