+ Networking

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The NEXUS STAR router is networked using only RFOC fibre-optic interface boards and duplex fibre-optic cables. This approach enables a variety of network setups to be implemented, for example, star topologies with parallel and redundant fibre-optic lines between Base Devices.
The NEXUS Base Device network is an entity: All inputs, outputs, and processing channels can be accessed and operated from anywhere on the routing system. In the control program, a single crosspoint simply connects an input to an output — it is up to the system to establish the fastest connection on the Base-Device network.

Optical Lines

The optical lines between Base Devices are always bidirectional, carrying a total of 256 audio channels plus control and sync information. The number of audio channels per direction is variable: either 128 are transferred in each direction, or assymetric set-ups with 192/64 or 64/192 channels are used.
Fibre-optic cables are convenient in mobile applications, too: Despite their immense transmission capacity, they are thin and light-weight. The galvanic separation established by optical lines avoids groundloops and confers increased electrical safety. Fibre-optic cables can span several thousand meters without signal loss and are insusceptible to electromagnetic and electrostatic interference. Therefore, new cables can be run in existing cable channels with no requirement for shielding.

+ System Size

A system can offer a maximum of 65,536 I/Os. It allows for routing up to 4,096 input channels to any number of outputs at the same time. This enables systems to be created that cover all possible applications from simple format converters in a studio to fully networked broadcasting complexes and even complete exhibition-centre networks.
The optimum network structure and the number of fibre-optic connections required are determined during the planning stage. For example, the network structure depends on the physical location of the Base Devices and on the routing capacity required.

+ Signal Distribution

On NEXUS STAR, inputs are routed to outputs using the RCX active routing matrix. The matrix centrally manages all audio channels of the interface boards (up to 16) installed into NEXUS STAR.
Connections are created dynamically, i.e. routing capacity is allocated for actual routing connections only. Therefore, the number of physical I/Os on the network can exceed considerably the already large number of 4,096 routable channels.

+ Synchronisation

In accordance with the NEXUS philosophy, NEXUS STAR operates fully in sync. This allows for a constant and short delay of all routed signals: the latency is just 6 samples. This figure makes NEXUS STAR perfectly suitable for time-critical applications where minimum latency is a must (e.g. live broadcasting).
The incoming sync clock is processed on the RCX controller board to ensure a low-jitter Base Device clock. This clock signal is made available at the wordclock output of the STAR router for use as a studio master clock or synchronising external recorders.
The absence of the requirement for a separate wordclock network simplifies the installation of large-scale systems and mobile operation.

Sample Rates

The NEXUS STAR routing system operates with the standard sample rates of 44.1 or 48 as well as 88.2 and 96 KHz. The NEXUS network sample rate is selected using the NEXUS software running on a control computer.

Sync Sources

The following sync sources on NEXUS STAR and the NEXUS Base Devices can be used for synchronising the NEXUS network:

  • Any wordclock input
  • Any digital input
  • The internal clock generator
  • Any optical input
  • The optional RSYNC board (video, WCLK, AES/EBU, SDI)
  • MADI (RMF) if available

The clock signal of an external source is processed on the NEXUS STAR RCX controller board or the XCPU controller board of any connected Base Device and is then distributed on the NEXUS network as a low-jitter clock.

Generator

The clock generator integrated on the control boards is based on a precision quartz crystal oscillator and can be used as a master clock for the entire studio. The standard version provides a frequency accuracy of better than ±10 ppm, thus meeting the requirements of AES-11, grade 2.

Auto Sync Search

At sync-source failure, NEXUS STAR and the NEXUS network will automatically select another clock source. The change occurs smoothly and without interruption. If no legitimate sync source is found (for example, because inappropriate sample rates are used), the system will switch to the internal clock generator of NEXUS STAR or a Base Device.
A freely configurable priority list determines the order of up to eight sync sources considered for auto sync search.

+ Hot Swap

All NEXUS STAR boards apart from the RCX boards, can be replaced while the system is in use. This allows for immediate servicing without shutdowns. Inadvertent installation of boards into unsuitable slots will not cause any damage. Failed, inappropriately installed, or missing boards are displayed on the user interface.

+ Power Supply

NEXUS STAR is a highly energy-efficient system. Even when fully populated, it requires a mere 200 W. Switch-mode, wide-range power supply units are mounted onto the router back panel. Operation with redundant supply units and automatic supply takeover is a standard feature; for this purpose, up to four power supplies can be connected to the router backplane. When a power supply fails, changeover is performed automatically and seamlessly.
While no NEXUS Base Device uses forced ventilation, attention must be paid to ensuring NEXUS STAR has sufficient air supply and circulation due to the high component density. In thermally critical areas, air-conditioning should be considered seriously.

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