If you manage a commercial building in New York, there’s a good chance someone has mentioned DAS to you — maybe a fire marshal, a tenant complaining about dead cell zones, or a consultant flagging it during a code review. The acronym gets thrown around alongside ERRCS, ARCS, and public-safety radio, and the terminology overlaps enough to confuse anyone who isn’t a low-voltage engineer.
This guide explains what a DAS system is, how it works, when a building actually needs one, and what New York code requires — without the jargon wall.
What is a DAS system?
A DAS — Distributed Antenna System — is a network of spatially separated antenna nodes connected by fiber or coaxial cable to a central signal source, designed to distribute cellular and radio signals throughout a building or campus where outdoor signals can’t penetrate.
Think of it as a relay system. Large commercial structures — high-rises, hospitals, stadiums, underground parking garages, warehouses, and data centers — are built with concrete, steel, and low-e glass that block RF signals. A phone that works fine on the sidewalk drops to zero bars the moment you walk into the building’s core. A DAS solves this by capturing signal from a donor antenna on the roof (or a direct carrier feed) and rebroadcasting it through a network of indoor antennas distributed across every floor.
The “distributed” part is key: instead of one powerful antenna blasting signal from a single point (which creates coverage hot spots and dead zones), a DAS uses many low-power antennas placed strategically so coverage is uniform. A phone call started at the elevator bank stays connected as you walk to the interior conference room.
What does DAS stand for?
DAS stands for Distributed Antenna System. The term originates from telecommunications engineering and is governed by a combination of FCC regulations (for cellular signal amplification) and fire codes (for public-safety radio coverage, often referred to separately as ERRCS — Emergency Responder Radio Communication Systems).
The two acronyms — DAS and ERRCS — are related but not interchangeable:
- Cellular DAS improves cell phone coverage for building occupants (tenants, employees, visitors). It’s optional from a code perspective but increasingly expected in Class A commercial space. Cellular DAS requires carrier approval from AT&T, Verizon, T-Mobile, or whoever’s signal you’re amplifying.
- Public-safety radio systems / ERRCS support first responders’ two-way radio communications inside buildings. Whether a system is required, and its design and acceptance criteria, depend on the applicable jurisdiction and project. NYC’s ARCS framework must be checked separately from a generic ERRCS specification.
A building can have one, both, or neither. Identify the cellular service objective separately from any public-safety radio requirement. Proposed alterations or changes of use need their own review under the applicable code.
How does a distributed antenna system work?
A DAS has four main components:
1. Signal source
The signal has to come from somewhere. There are two options:
- Off-air donor antenna — a directional antenna on the roof pointed at the nearest cell tower. This captures the outdoor signal and feeds it into the system. It’s cheaper and faster to deploy, but performance depends on the quality of signal at the roof.
- Direct carrier feed — a fiber or coax connection directly from the carrier’s network, brought into the building via a meet-me room or fiber handoff. This is the enterprise-grade option used in large buildings and stadiums where off-air signal isn’t reliable enough. It requires a commercial agreement with each carrier.
2. Head-end equipment
The head-end is the brain of the system. It sits in a telecommunications room (often the MDF) and consists of:
- Signal processing units — amplifiers, filters, and combiners that clean up the incoming signal, split it into bands (one for each carrier or frequency), and distribute it to remote units
- Optical transceivers — convert the RF signal to light for distribution over fiber (in active DAS) or keep it as RF for coax distribution (in passive DAS)
- Monitoring equipment — network management systems that alarm when an antenna goes down or signal degrades
3. Distribution network
This is the cabling that carries signal from the head-end to the antennas. There are three DAS architectures:
- Passive DAS — coaxial cable from the head-end to every antenna. Simple, reliable, no active electronics between head-end and antenna. Best for smaller buildings (under ~100,000 sq ft) where cable runs are short enough that signal loss over coax is manageable.
- Active DAS — fiber optic cable from the head-end to remote amplifier units (RAUs) on each floor, then short coax runs from RAUs to antennas. The RAUs actively amplify the signal, allowing longer runs and larger buildings. This is the standard for high-rises, hospitals, and campuses.
- Hybrid DAS — a mix of fiber backbone and coax distribution, balancing cost and performance. Common in mid-size buildings.
4. Indoor antennas
These are the visible endpoints — small ceiling-mounted or wall-mounted antennas (often disguised as smoke detectors or ceiling tiles in aesthetic-conscious spaces) that broadcast the signal into the occupied area. A typical floor might have 4-12 antennas depending on size, layout, and construction.
Active vs. passive DAS: what’s the difference?
The architecture choice comes down to building size, budget, and signal requirements:
| Passive DAS | Active DAS | |
|---|---|---|
| Distribution | Coax only | Fiber + RAUs + coax |
| Building size | Under ~100K sq ft | 100K sq ft to millions |
| Signal loss | Higher (coax attenuates over distance) | Low (fiber doesn’t attenuate RF) |
| Cost | Lower ($1-3/sq ft) | Higher ($3-8/sq ft) |
| Scalability | Limited by coax run lengths | Highly scalable |
| Maintenance | Simple (no active electronics in the field) | RAUs need power + monitoring |
| Best for | Small offices, retail, warehouses | High-rises, hospitals, stadiums, campuses |
There’s also digital DAS (sometimes called micro DAS), which digitizes the RF signal at the head-end and distributes it over fiber or copper as digital data, converting back to analog only at the antenna. This is newer technology that reduces noise, allows precise per-antenna power control, and is gaining traction — especially in buildings where RF interference between antennas is a concern.
Does my building need an ERRCS?
Start with the jurisdiction, applicable code edition, building conditions and proposed work. New York State’s 2025 Uniform Code took effect December 31, 2025; New York City has its own building-code framework. The Department of State’s code FAQ explains that distinction. A generic square-footage threshold or signal-coverage percentage is not a project-specific determination.
In NYC, ARCS (Auxiliary Radio Communication System) is addressed by Building Code BC 916, Fire Code FC 510 and FDNY rule 3 RCNY 510-01. FC 510 addresses systems dedicated to fire-department use, including commissioning and department acceptance. It is a separate scope from improving tenants’ cellular reception.
Existing-building alterations also need review. DOB Buildings Bulletin 2024-001 identifies alteration circumstances that can trigger ARCS and references FDNY determinations under BC 916.3. Have the project design team establish the applicable requirement and acceptance path before pricing a system. A passing mobile-phone test does not settle an ARCS requirement. Read our FDNY ARCS guide for the scope and documentation questions.
What does a DAS or ERRCS installation cost?
Cost varies widely based on building size, architecture (active vs. passive), number of carriers supported (cellular DAS only), and the existing pathway infrastructure:
- ERRCS (public-safety) — $2-5 per square foot for a typical commercial building. A 50,000 sq ft office might run $100K-250K. High-rises and hospitals cost more per square foot due to complexity.
- Cellular DAS — $3-8 per square foot for an active system. A 200,000 sq ft Class A office might run $600K-1.6M. Carrier cost-sharing agreements can offset this — carriers often contribute infrastructure or ongoing fees in exchange for exclusive or shared access.
- Micro DAS / digital DAS — $2-5 per square foot, but with lower per-antenna costs at scale. Best for buildings that need cellular coverage but can’t justify full active DAS pricing.
The ERRCS cost is non-negotiable if code requires it — you won’t get a certificate of occupancy without passing the acceptance test. Cellular DAS is a business decision: tenants in Class A space expect it, and buildings without it lose leasing velocity.
How long does a DAS or ERRCS project take?
From survey to sign-off, expect:
- RF survey (1-2 weeks) — measure existing signal throughout the building, identify dead zones, determine coverage requirements
- System design and engineering (3-6 weeks) — antenna placement, head-end location, cable routing, power and monitoring design
- Carrier coordination (cellular DAS only, 4-12 weeks) — each carrier must review and approve the design before installation. This is often the longest lead time.
- Installation (4-12 weeks) — cable pulls, head-end build, antenna mounting, RAU installation
- Acceptance testing (1-2 weeks) — signal strength verification, fire marshal sign-off (ERRCS) or carrier acceptance (cellular DAS)
Total timeline: 3-6 months for ERRCS, 6-12 months for cellular DAS (carrier coordination dominates). If you’re building a new building, start the DAS conversation during design — not after the walls are closed.
What to look for in a DAS installer
Not every low-voltage contractor can design and install a DAS. The work requires specialized equipment (spectrum analyzers, signal generators, PIM testers), familiarity with carrier approval processes, and for ERRCS, relationships with the local fire marshal’s office and AHJ (Authority Having Jurisdiction).
Look for:
- iBwave certification (the industry-standard DAS design tool)
- Carrier-approved status with AT&T, Verizon, and T-Mobile for cellular DAS
- ERRCS experience in your jurisdiction — every fire marshal interprets the code slightly differently
- Manufacturer partnerships with major DAS OEMs (CommScope, Corning, JMA Wireless, Zinwave, Solid)
- References from similar building types — a DAS in a hospital is different from one in a warehouse
The bottom line
A DAS system distributes radio signals within a building or campus. For a New York project, establish the applicable public-safety requirement with the design team and authority having jurisdiction, and assess cellular coverage as a separate user need. A survey informs the design; it does not replace the required code determination, approvals or acceptance process.
Scoping a DAS or ERRCS project anywhere in New York? Get a Free Estimate — share the site and scope so we can assess a match with a partner contractor appropriate to the project requirements.