The Avari Wireless VL‑RU 33/37 is a high‑power, modular remote radio unit that forms the critical last‑mile link in the Avari VL™ Series digital Distributed Antenna System (DAS). Designed specifically for Emergency Responder Communications Enhancement Systems (ERCES), the VL‑RU 33/37 converts digital optical signals back into RF across 1 to 3 public safety bands simultaneously, with 2 W (VL‑RU 33) or 5 W (VL‑RU 37) of output power per band. Its pluggable RF modules, lossless digital transport, and advanced FPGA‑based digital signal processing differentiate it from analog or lower‑order digital DAS solutions, especially in electrically quiet environments where signal fidelity and regulatory spectral compliance are critical. The unit's fanless, convection‑cooled IP66/NEMA 4 enclosure, combined with NFPA‑compliant dry‑contact alarm connections, makes it suitable for indoor and outdoor installations in tunnels, metros, airports, stadiums, and other large, complex environments where life‑safety communications are non‑negotiable.

Lossless Digital Transport and Signal Processing

• Long‑distance Fiber with Automatic Optical Delay Compensation (AODC): Utilizing a digital transport backbone over single‑mode fiber, the VL‑RU 33/37 receives signals from a centralized headend unit over distances exceeding several kilometers with no degradation or increase in noise floor typical of analog coaxial or radiating cable systems. The integrated Automatic Optical Delay Compensation (AODC) automatically measures signal arrival time at each remote unit and equalizes it, mitigating time‑delay interference (TDI) critical for narrowband P25 systems and LTE MIMO applications.
• Advanced Digital Signal Processing for Superior Audio: A Field‑Programmable Gate Array (FPGA) chipset performs channelized, Class‑A digital filtering with up to 64 software‑configurable channels. This fine‑grained filtering ensures that strong adjacent signals do not desensitize the remote unit, maintaining clear audio and reliable data communication even in congested RF environments. The digital filtering also eliminates the passive intermodulation (PIM) issues that plague analog DAS installations, reducing site installation costs and commissioning time.
• Pluggable Band Modules for Future‑Proofing: The VL‑RU 33/37 accommodates up to 3 frequency bands simultaneously via field‑replaceable and software‑configurable RF plug‑in modules. This modular architecture supports all major public safety frequency bands—VHF, UHF, 700 MHz, 800 MHz, and 900 MHz—and standards including P25 Phase I and II, TETRA, DMR, GSM‑R, and LTE. As public safety agencies transition from legacy LMR to FirstNet and other LTE‑based technologies, the VL‑RU 33/37 can be upgraded via software image uploads without requiring hardware replacement, effectively future‑proofing the investment.

Redundant, Self‑Healing Network Topology for Mission‑Critical Uptime

• End‑to‑End Fiber Redundancy: The VL‑RU 33/37 supports dual fiber feeds from disparate or redundant headend locations, enabling true end‑to‑end redundancy. In the event of a fiber cut, hardware failure, or local power outage, the system detects the fault and automatically switches to the redundant fiber path within milliseconds, ensuring uninterrupted emergency communications. This self‑healing capability operates without manual intervention, a critical requirement for first responder systems where every second counts.
• Flexible Topology for Complex Deployments: The digital transport architecture supports multiple fiber topologies—star, daisy‑chain, ring, and hybrid—allowing system designers to optimize fiber utilization and cost while maintaining redundancy across the network. For tunnel applications, the daisy‑chain topology allows a single fiber pair to serve multiple remote units along the tunnel length, dramatically reducing fiber installation costs. For campus environments, the star topology provides centralized management and simplified troubleshooting.
• Centralized Management with VL‑EM™: The entire Avari VL™ network is managed by the VL‑EM™ Element Manager, a centralized platform that provides real‑time fault monitoring, performance analytics, and configuration management for every remote unit in the system. The VL‑EM™ supports industry‑standard SNMP for integration with existing network management systems, and its built‑in web server allows secure access from any browser without requiring dedicated client software.

NFPA‑Compliant Design for Fire Protection Integration

• Integrated Fire Alarm Connectivity: All VL‑RU 33/37 units include dedicated dry‑contact alarm connections compliant with NFPA (National Fire Protection Association) fire code standards. These connections allow the DAS to integrate directly with a building's fire alarm control panel, providing positive confirmation of system integrity and immediate alarm notification in the event of a DAS component failure. Avari's flexible alarm connection solution supports both centralized and distributed fire alarm panels, an architectural flexibility not commonly found in competitor DAS systems.
• Fanless, Convection‑Cooled Enclosure: The IP66/NEMA 4‑rated enclosure relies entirely on natural convection for heat dissipation, eliminating the need for fans or active cooling. This design choice removes a common point of mechanical failure, reduces maintenance requirements, and ensures silent operation suitable for noise‑sensitive indoor environments such as hospital emergency rooms, concert halls, and luxury hotel lobbies where ERCES must operate transparently.
• Indoor and Outdoor Rated: The robust enclosure design allows the VL‑RU 33/37 to be deployed in a wide range of environments, from climate‑controlled equipment rooms to unconditioned outdoor cabinets exposed to rain, dust, and temperature extremes. This deployment flexibility simplifies system design and reduces the need for additional protective enclosures or environmental controls at remote unit locations.

Applications

• Railway and subway tunnel communications: providing seamless coverage for transit operations, maintenance crews, and emergency responders
• Airports: ensuring uninterrupted public safety radio coverage across terminals, concourses, and baggage handling areas
• Sports stadiums and large arenas: delivering high‑capacity multi‑band coverage for security, medical, and event operations personnel
• High‑rise commercial buildings: overcoming signal attenuation caused by low‑E glass, steel framing, and concrete construction
• Hospital and healthcare campuses: supporting critical communications for emergency departments, operating rooms, and facility management
• University and corporate campuses: providing wide‑area coverage for campus security and emergency management teams
• Any medium to large‑scale indoor or outdoor deployment requiring a mission‑critical, NFPA‑compliant public safety DAS with self‑healing redundancy