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Intercom

An intercom is a two-way communication system with a microphone and loudspeaker at each station for localized use, typically within a building or limited area.^[1] Also known as an intercommunication device, intercommunicator, or interphone, it enables voice exchanges between multiple points without relying on external telephone networks.^[2] Modern intercom systems often incorporate video capabilities, digital controls, and integration with IP networks or wireless technologies for enhanced functionality.^[3] They are commonly applied in residential and commercial buildings for internal communication and access control, in broadcasting and production environments for team coordination, and in transportation such as trains, aircraft, and emergency vehicles.^[4]

Fundamentals

Definition and Functionality

An intercom is a stand-alone voice communications system designed for use within a building, vehicle, or small campus, typically supporting two-way audio exchange between multiple stations.^[5]^[4] This setup enables direct, localized interaction without reliance on external networks, facilitating efficient coordination among users in close proximity.^[2] Primary functionalities of an intercom include hands-free or push-to-talk modes for real-time conversations, broadcasting announcements to selected or all stations, and integration with access control mechanisms, such as authorizing door entry for visitors.^[6]^[4] These features support applications like internal coordination in offices, security monitoring in residential complexes, or operational directives in industrial settings.^[7] Intercoms differ from telephone systems, which connect users over long distances via public switched telephone networks, and from public address systems, which deliver one-way audio announcements without response capability; instead, intercoms prioritize bidirectional, short-range voice communication within defined spaces.^[8]^[9] At their core, intercoms operate by capturing audio at one station, transmitting it through dedicated wired lines or wireless channels to receiving stations, and reproducing it with amplification to maintain clarity amid ambient noise.^[10]^[11] This process has transitioned from analog signal handling to digital formats for enhanced audio quality and reduced interference.^[12]

Key Terminology

In intercom systems, the term intercom derives from "intercommunication," a shortening that emerged in the early 20th century to describe devices or networks facilitating reciprocal audio exchange between users.^[13]^[14] A station refers to an endpoint device in an intercom network, typically incorporating a microphone, speaker, and controls for user interaction, serving as the primary interface for sending and receiving audio.^[15] In practice, stations range from fixed wall-mounted units to portable models, enabling connection to communication channels.^[16] The concept of a party line denotes a shared communication channel where multiple stations are connected in parallel, allowing all participants to transmit and receive audio simultaneously in a conference-style setup.^[15] This full-duplex arrangement supports group coordination without dedicated point-to-point links, commonly used in production environments.^[16] IFB, or interruptible foldback, is a specialized audio feed in broadcast intercoms that delivers program audio to talent while permitting interruption by a director or producer for cues and instructions, often via an earpiece.^[15] The term "foldback" originates from audio engineering practices where monitor mixes are "folded back" to performers, with "interruptible" emphasizing the override capability.^[16] In intercom contexts, full-duplex communication enables simultaneous transmission and reception of audio between parties, akin to a natural conversation where interruptions are possible.^[15] By contrast, half-duplex operation restricts communication to one direction at a time, requiring users to alternate speaking and listening, similar to traditional walkie-talkies.^[16] A matrix functions as a central switching system in advanced intercom setups, routing audio paths dynamically between multiple stations via a digitally controlled frame, often using time-division multiplexing for efficient handling of numerous connections.^[15] This architecture supports scalable, configurable networks beyond simple shared lines.^[16] The master station acts as the central control unit in an intercom system, typically integrating power supply, multiple channels, and oversight functions to manage connected devices.^[15] Complementing this, a slave station is a subordinate remote unit that relies on the master for power and signaling, lacking independent control.^[16] Finally, a beltpack is a compact, wearable transceiver designed for portability, featuring headset connectivity and worn on a user's belt to enable hands-free operation in dynamic settings like stage production.^[15] These units connect via cables to the main system, prioritizing mobility for crew members.^[16]

Historical Development

Origins and Early Systems

The development of intercom systems in the early 20th century built upon telephone technology, with significant advancements occurring in the 1920s and 1930s for industrial and broadcast applications. One of the earliest patented electrical intercom systems was developed by the Kellogg Switchboard and Supply Company in 1894, featuring a circuit with signaling panels for apartment buildings to alert residents via buzzing. A few years later, earpieces and mouthpieces were added for two-way communication.^[17] By the 1930s, innovations included the Loudaphone system, designed for noisy industrial settings, which employed noise-cancelling features to enable clear voice transmission over shared wiring.^[18] Additionally, Allan C. Bernstein founded Adams Laboratories (later Executone) in the late 1930s, introducing compact two-station setups for office "boss-to-secretary" coordination and hospital "patient-to-nurse" alerts, marking a shift toward specialized wired communication tools.^[18] Initial applications of these systems appeared in demanding environments like shipboard operations and theaters, relying on basic microphone-speaker configurations connected via shared wires. On ships such as the RMS Queen Mary, the Loudaphone was installed in engine rooms during the 1930s to facilitate communication amid high noise levels, using robust speakers and microphones to bridge distances between crew stations without relying on acoustic tubes.^[18] In theaters, early electrical intercoms supplemented traditional speaking tubes, with handset-based units placed backstage and in control booths to allow directors and technicians to exchange cues and instructions over simple wired networks, improving coordination during live performances.^[19] These setups typically involved low-impedance circuits to minimize signal loss over the shared wiring, enabling reliable point-to-point or multi-station audio exchange in real time. A pivotal milestone came in the 1930s with the adoption of party-line systems in early television broadcasting, adapted from telephone infrastructure to enable simultaneous coordination among directors, engineers, and crew. Broadcasters like NBC and CBS improvised these systems using telco-derived party lines, where multiple stations shared a single audio channel for group communication, essential for synchronizing live transmissions and cueing talent without dedicated lines for each role.^[20] This approach, often involving basic switchboards, allowed for efficient, hands-free operation in studios, setting the foundation for scalable broadcast intercoms and highlighting the limitations of early analog sharing, such as crosstalk in busy scenarios. At their core, these analog wired intercoms operated on low-voltage DC signaling to power devices and alert users, superimposed on audio lines for efficient transmission. A central power supply delivered 18-32 VDC through the wiring, with call signals generated using superimposed high-frequency tones (e.g., 20 kHz) or DC shifts to activate lights at remote stations without interfering with voice paths.^[15] Audio was captured using carbon microphones, which modulated electrical current via compressed carbon granules under a diaphragm, providing high-output signals suitable for early amplifiers and shared lines, though prone to distortion in humid or noisy conditions.^[21] These elements ensured reliable, low-cost operation in pre-vacuum-tube eras, powering the foundational role of intercoms in coordinated environments.

Evolution to Digital and IP

The transition from analog to digital intercom systems began in the 1970s and accelerated through the 1980s, driven by the need to address limitations of early wired setups, such as signal degradation over long distances and susceptibility to noise in broadcast environments.^[20] Digital signaling was adopted to enable noise reduction through techniques like low-noise preamplifiers and frequency-specific call lights (e.g., 20 kHz for signaling), improving audio clarity and reliability.^[22] Pioneering systems from manufacturers like RTS introduced bilateral current sources for seamless channel switching without DC bias, while Clear-Com launched its first digital matrix intercom, Matrix Plus, in the early 1980s, supporting matrix switching for configurable routing in large-scale installations. Digital matrix systems employed Time Division Multiplexing (TDM) for efficient audio routing and switching among multiple users.^[23]^[22] By the 1990s, the integration of Internet Protocol (IP) technologies marked a further evolution, with Voice over IP (VoIP) protocols such as Session Initiation Protocol (SIP) enabling intercoms to operate over Ethernet networks and leverage existing infrastructure for voice communication.^[24] This shift allowed for networked systems that expanded beyond traditional party-line limitations, supporting remote connectivity and reducing the need for dedicated cabling.^[20] Key advancements in the 2000s included the adoption of digital wireless standards like DECT (Digital Enhanced Cordless Telecommunications), which provided license-free spectrum for mobile communication while maintaining digital audio quality.^[25] In the 2010s, cloud-managed systems emerged, offering centralized control and remote access through internet-based platforms, further enhancing integration with broader IP ecosystems.^[24] These developments delivered significant benefits, including reduced cabling costs by utilizing standard Ethernet, improved scalability for installations supporting hundreds of users, and hybrid compatibility that allowed seamless integration of analog and digital components.^[26]^[20]

System Components

Hardware Elements

Intercom systems rely on a variety of core hardware components to facilitate audio communication, including microphones, speakers, amplifiers, and control panels. Microphones, essential for capturing user input, come in dynamic types with impedances typically ranging from 150 to 500 ohms, which are robust against magnetic interference, and condenser or electret variants requiring 1-5V excitation and offering higher sensitivity with impedances of 1000-2000 ohms.^[15] Speakers, integrated into stations for audio output, often feature dimming capabilities to minimize feedback, while amplifiers—such as headphone amplifiers providing 30-40 dB gain or speaker amplifiers handling 2-45 ohm loads—boost signals from microphone level to line level for clear transmission.^[15] Control panels, functioning as central interfaces, incorporate buttons for talk/listen functions, displays for status indication, and sometimes removable microphones, enabling users to manage multiple channels in professional setups.^[15] Station types vary to suit different environments, encompassing wall-mounted units for fixed installations, desktop consoles for flexible operation, and headset-compatible belt packs for mobile use. Wall-mounted stations, such as the SS1002 model, provide durable, space-efficient options with built-in speakers and microphones for locations like control rooms.^[15] Desktop consoles, including portable speaker stations like the MRT327, offer ergonomic designs with modular mounting for desks or racks, supporting multi-channel access.^[15] Belt packs, such as the BP319 or BP325, are compact, wearable devices that connect to headsets, delivering binaural audio and high sound pressure levels for on-the-move communication in production or industrial settings.^[15] These stations often designate master units for centralized control and slave units for remote access, aligning with standard intercom terminology.^[15] Components vary by application; simpler residential or door entry systems may use basic unamplified speakers and buzzers without advanced controls. Connectivity hardware ensures reliable integration of system elements, including patch panels, power supplies, and specialized cabling. Patch panels, like the SAP1626 or BOP220 with 20 jacks, allow reconfiguration of connections without rewiring, facilitating channel assignments in matrix systems.^[15] Power supplies, such as the PS2001L (1RU rack unit) or PS31 (2RU for six channels), deliver centralized DC power at voltages like 32 VDC to stations and belt packs, supporting distributed amplification.^[15] Cabling typically employs shielded twisted pair, such as 22 AWG microphone cable or Belden 8723, to minimize crosstalk and handle distances limited by capacitance and resistance, ensuring low-noise audio transmission.^[15] Specialized hardware addresses niche applications, including gooseneck microphones for permanent installations and ruggedized units for demanding environments. Gooseneck microphones provide adjustable, directional pickup in fixed stations, ideal for podiums or desks in conference settings.^[15] Ruggedized units, such as reinforced belt packs like the BP325 or lightweight matrix frames like the ODIN, feature durable construction for high-noise or field use, including events requiring robust 24-port connectivity.^[15]^[27] These elements enhance system versatility without compromising audio integrity.

Software and Control Features

Control software for intercom systems primarily revolves around digital matrix platforms that enable efficient call routing and management. In professional setups, such as those from Clear-Com's Eclipse HX, the EHX configuration software employs matrix routing algorithms to facilitate point-to-point, partyline, and group communications, allowing non-blocking bidirectional audio paths across networked matrices.^[28] Similarly, RTS's AZedit software supports dynamic port assignment and user reallocation within matrix frames like ADAM and ODIN, optimizing call assignment in real-time for broadcast and live production environments.^[29] These algorithms ensure scalable connectivity, often handling hundreds of simultaneous connections without latency, and interface briefly with hardware elements like keypanels for seamless operation.^[30] Volume and gain controls are typically managed through graphical user interfaces (GUIs) that provide intuitive adjustments for audio levels. EHX, for instance, allows administrators to enable, limit, or disable gain on individual devices via its Windows-based GUI, supporting both online and offline modifications without interrupting live communications.^[28] AZedit offers comparable functionality with dedicated panels for input/output level calibration, ensuring balanced audio distribution across the system.^[31] Such controls are essential for maintaining clarity in high-noise environments like theaters or control rooms. Key features enhance operational efficiency and security in these systems. Programmable hotkeys, configured on keypanels, allow users to assign talk/listen functions to specific buttons for rapid access to frequent contacts, as seen in RTS KP-series panels with up to 32 customizable lever keys.^[32] User authentication is implemented through tiered access levels; EHX provides four levels—Guest, User, Local, and Admin—to restrict configuration changes and secure IP-connected clients.^[28] In IP-based systems, logging capabilities record call events, system diagnostics, and health metrics, enabling audit trails and troubleshooting, as supported by EHX's telemetry from wireless beltpacks.^[28] Integration tools extend intercom functionality beyond isolated networks. APIs, such as Commend's SymMX interface, enable linkage to building management systems (BMS) for automated responses like door releases or alarm triggers tied to intercom events.^[33] Firmware updates for digital units are handled via dedicated software modules; for example, AZedit and EHX support over-the-air or USB-based upgrades to incorporate new protocols like SIP or AES67 without hardware replacement.^[29]^[28] User interfaces have evolved to include modern options for configuration and monitoring. Touchscreen panels, integrated into systems like Clear-Com's multi-function operator interfaces, offer role-based workflows with up to 2x10 customizable displays for quick navigation.^[28] Mobile apps, such as Clear-Com's Agent-IC, provide remote access for setup and participation, allowing users to join intercom sessions via smartphones over Wi-Fi or cellular networks, complementing traditional desktop GUIs.^[34] These interfaces prioritize accessibility, with client/server architectures in EHX enabling multiple users to collaborate on configurations simultaneously.^[28]

Wired Intercom Systems

Two-Wire Systems

Two-wire intercom systems utilize a single pair of wires to transmit both audio signals and DC power for signaling, enabling bidirectional communication over a shared circuit. This design typically employs unbalanced audio lines (single-ended with DC bias) to minimize electromagnetic interference and noise, with the two conductors serving dual purposes: one for the audio signal and the other as a common return path, often combined with a DC bias voltage to control call signals and microphone gating. These systems typically operate at 24-30V DC with audio bandwidth of 300 Hz to 8 kHz.^[15] The simplicity of this architecture makes two-wire systems advantageous for installations requiring minimal cabling, reducing material costs and labor compared to more complex setups. They are particularly cost-effective for small-scale applications, such as residential apartments, basic production environments, or entry-level broadcast facilities, where ease of deployment outweighs advanced performance needs. In practice, two-wire systems often form the backbone of party-line configurations, allowing multiple users to connect on a shared audio bus for group communication. Examples include Clear-Com's Encore Analog Partyline and RS-series systems, which provide reliable, low-latency audio distribution in theater and event productions.^[35] However, these systems have inherent limitations, including the risk of crosstalk in multi-station environments due to the shared line, which can degrade audio clarity when multiple parties transmit simultaneously. Additionally, their half-duplex nature restricts full-duplex conversation, as the circuit cannot support independent send and receive paths without external enhancements.

Four-Wire Systems

Four-wire intercom systems employ a design that utilizes two separate pairs of wires—one pair dedicated to transmitting audio and the other to receiving audio—along with ground connections to establish independent channels for bidirectional communication.^[15] This configuration, often implemented in a point-to-point or star topology connected to a central matrix, supports full-duplex operation over extended distances, such as up to two miles using #22 gauge twisted-pair cabling.^[15] Unlike simpler wired options that share infrastructure, four-wire setups provide dedicated paths that enhance signal integrity in demanding environments.^[36] The primary advantages of four-wire systems include their inherent full-duplex capability, which allows simultaneous transmission and reception without interruption, making them ideal for real-time coordination.^[15] They also offer superior noise isolation through balanced lines and separate audio paths, minimizing interference and crosstalk in high-fidelity applications.^[15] Additionally, these systems scale effectively via matrix architectures, accommodating large configurations with hundreds of ports for complex operations.^[15] Technically, four-wire intercoms standardize on XLR connectors, such as three-pin or four-pin variants, to ensure robust, professional-grade interconnections that support balanced audio transmission.^[15] Hybrid circuits are integral to their operation, functioning to separate incoming and outgoing signals and prevent feedback by nulling sidetone, as seen in interfaces like the RTS SSA-424.^[15] These circuits often employ automatic balancing to maintain clear audio even under varying loads.^[22] In professional broadcast environments, four-wire systems are prevalent in TV studios and mobile production units, where systems like RTS ADAM matrices support over 1,000 ports for network trucks and control rooms.^[15] Telex implementations, such as those integrated with RTS, have been deployed in high-profile setups including KNBC news trucks and ESPN production vehicles, enabling seamless communication for directors, camera operators, and talent.^[22]^[15]

Wireless Intercom Systems

Radio-Frequency Based

Radio-frequency (RF) based wireless intercom systems utilize ultra-high frequency (UHF, typically 400-900 MHz) or very high frequency (VHF, 30-300 MHz) bands to enable untethered, full-duplex communication in professional environments such as stage production and live events. These systems consist of a central base station connected to wired intercom networks or audio sources, which relays signals to portable beltpack transceivers worn by users. The base station transmits downlink signals to all beltpacks on a shared frequency, while each beltpack uses a unique uplink frequency to send audio back, allowing multiple users to communicate simultaneously without interruption. Operating ranges generally span 100-500 meters in open areas, influenced by transmit power, antenna design, terrain, and environmental obstructions, though actual performance often falls to 50-150 meters in complex indoor venues like theaters.^[37]^[38]^[39] A primary advantage of RF-based systems is their high mobility, enabling crew members in stage and production settings to move freely across large areas without the constraints of cabling, which is particularly beneficial for dynamic environments like concerts or theater setups where quick repositioning is essential. Installation is simplified as no extensive wiring is required, reducing setup time and costs for temporary or portable applications compared to wired alternatives. These systems support seamless integration with existing partyline or matrix intercom infrastructures, providing reliable hands-free operation via headsets attached to beltpacks.^[40]^[41] However, RF systems are prone to interference from other wireless devices, television broadcasts, or environmental factors, which can degrade audio quality or cause dropouts in crowded frequency spectra. Use of licensed UHF or VHF bands often requires FCC coordination in the United States to avoid conflicts with broadcast services, adding regulatory complexity and potential costs. Additionally, beltpack operation relies on rechargeable batteries, introducing dependency on power management to prevent communication failures during extended use.^[37]^[42]^[43] Prominent examples include analog UHF systems like the RTS BTR-700, a single-channel base station supporting up to four beltpacks for basic partyline communication in theater applications. Early digital variants, such as the RTS BTR-80 narrowband system, enhance audio clarity while maintaining UHF operation for two-channel setups in production environments. The Radio Active Designs UV-1G represents a VHF/UHF hybrid analog design optimized for stage use, employing narrow 25 kHz bandwidth to minimize spectrum congestion.^[41]^[37]^[44]

DECT and Other Standards

Digital Enhanced Cordless Telecommunications (DECT) is a standardized digital wireless technology primarily operating in the 1.88–1.93 GHz frequency band, enabling reliable short-range communications for applications including professional intercom systems.^[45] Developed and maintained by the European Telecommunications Standards Institute (ETSI), DECT employs time-division multiple access (TDMA) to support full-duplex audio transmission, allowing simultaneous two-way conversations without the need for separate frequencies for send and receive.^[46] It incorporates digital encryption protocols, such as DECT Standard Cipher, to secure communications against eavesdropping, and features handover mechanisms that enable seamless roaming between base stations as users move within coverage areas.^[47] Recent evolutions include DECT-2020 New Radio (NR), an ETSI standard extending capabilities to sub-6 GHz bands for enhanced IoT integration and low-latency applications as of 2024.^[48] Beyond DECT, other standards facilitate wireless intercom functionality tailored to specific needs. Bluetooth, operating in the 2.4 GHz ISM band, excels in short-range pairing for point-to-point or small-group intercom setups, commonly used in portable headsets for quick connections over distances up to 10–100 meters depending on the version (e.g., Bluetooth 5.0). Wi-Fi standards, such as IEEE 802.11, support data-integrated audio intercoms by leveraging existing network infrastructure for voice-over-IP (VoIP) transmission, enabling integration with broader digital ecosystems like SIP-based systems for multi-site or app-controlled communications.^[49] DECT-based intercoms offer key advantages, including license-free operation in allocated bands across many regions (e.g., 1880–1900 MHz in Europe and 1920–1930 MHz in the US), which reduces deployment costs and regulatory hurdles.^[46] They achieve low latency, typically under 100 ms due to the 10 ms TDMA frame structure, ensuring real-time conversational flow critical for professional environments. Additionally, DECT supports easy integration with cordless handsets, allowing users to switch between headset and handset modes while maintaining compatibility with IP networks for expanded coverage.^[50] Prominent examples of DECT intercom systems include the Riedel Bolero, which utilizes 1.9 GHz DECT for license-free, full-duplex wireless beltpacks in broadcast and event production, supporting up to 100 users with ADR technology to mitigate multipath interference.^[50] In marine applications, Vingtor-Stentofon IP DECT solutions from Zenitel provide rugged, handover-enabled intercoms for onboard ship communications, integrating with AlphaCom exchanges for voice and alarm distribution in harsh environments.^[51] For aviation, Clear-Com's FreeSpeak II employs DECT in the 1.9 GHz band to deliver low-latency, encrypted wireless intercoms for air traffic control and ground operations, with seamless base station handoff over large areas.^[46]^[52]

Integrated Intercom Solutions

Telephone Intercoms

Telephone intercoms integrate with traditional telephone infrastructure, such as Plain Old Telephone Service (POTS) or Private Branch Exchange (PBX) systems, to enable communication across extensions within a building or organization. These systems typically connect intercom stations to the PBX via dedicated lines or extensions, allowing users to dial specific numbers for internal calls without requiring external phone lines. For instance, in a VoIP-enabled PBX setup, intercom calls are routed as internal SIP extensions, leveraging the same network for both voice and signaling. This design facilitates seamless incorporation into existing telephony environments, where intercom units function as specialized endpoints on the PBX. In POTS-based systems, analog lines carry the audio signals, while modern VoIP integrations use packet-switched protocols for efficiency. The core mechanism involves assigning unique extension numbers to each intercom station, enabling selective calling through standard dialing interfaces. Key advantages of telephone intercoms include their ability to utilize pre-installed phone wiring and infrastructure, reducing the need for additional cabling in retrofitted buildings. Features like caller ID display the originating extension on receiving phones, aiding in quick identification, while dialing supports precise routing to individual or grouped stations. This approach also allows integration with broader PBX functionalities, such as call forwarding and voicemail, enhancing overall communication management. However, these systems are limited by the quality and availability of the underlying phone lines; signal degradation over long analog runs can introduce noise or echoes, impacting clarity. They are also less ideal for hands-free broadcasting to multiple parties simultaneously, as PBX routing prioritizes point-to-point connections over open-mic announcements. Practical examples illustrate their application in professional settings. In office environments, Avaya PBX systems support intercom extensions for departmental communication, where desk phones double as intercom units via programmable buttons. Similarly, apartment buildings often employ landline-tied buzzers connected to a central PBX, allowing tenants to receive visitor announcements directly on their home phones.

Cellular and Mobile Intercoms

Cellular and mobile intercoms leverage cellular networks to enable push-to-talk (PTT) communication for users in remote or mobile environments, providing instant voice exchanges without reliance on fixed infrastructure. This technology, known as Push-to-Talk over Cellular (PoC), integrates with 4G, LTE, and 5G networks to convert voice into digital packets transmitted via IP protocols, allowing seamless connectivity across wide areas.^[53]^[54] PoC systems operate through dedicated devices or mobile apps on smartphones, supporting features like one-to-one calls, group conferencing, and location sharing, with 5G enhancements reducing latency to near-real-time levels for more reliable interactions.^[55]^[56] A key advantage of cellular intercoms is their extensive coverage, utilizing existing cellular infrastructure to enable communication over national or even international ranges without the need for site-specific repeaters or base stations.^[57] This facilitates group calling capabilities via LTE and 5G, supporting large teams in industries like logistics and public safety, where users can connect instantly across dispersed locations.^[58] Additionally, PoC systems offer scalability and integration with other digital tools, such as GPS tracking, without high upfront hardware costs.^[59] Despite these benefits, cellular intercoms face limitations including dependency on network availability, which can lead to latency or dropped connections in areas with poor signal strength or congestion.^[60] Data usage incurs ongoing subscription fees from mobile operators, potentially increasing operational costs for high-volume communications.^[61] Security is another concern, as transmissions over public cellular networks require robust end-to-end encryption, such as AES standards, to prevent interception and ensure privacy.^[62]^[63] Prominent examples include Motorola Solutions' WAVE PTX platform, which provides PoC through a combination of apps and rugged devices for professional teams in construction and emergency services, enabling encrypted group PTT over 4G/5G.^[54] Similarly, the Zello app serves as an accessible PoC solution, adapted for workforce communication in sectors like transportation and security, where it supports unlimited channels and integrates with cellular data for real-time coordination.^[64]^[65]

Video and IP Intercoms

Video Integration

Video integration in intercom systems incorporates cameras and displays to enable visual verification of visitors alongside audio communication, allowing users to assess identities before granting access. This enhancement relies on precise audio-video synchronization, where video feeds from entry-point cameras align seamlessly with two-way audio streams to facilitate natural conversations without noticeable delays. Such systems typically operate over IP networks, ensuring low-latency transmission for real-time interaction.^[66] Key components include IP cameras embedded in door stations, which capture high-definition footage, video codecs such as H.264 and H.265 for efficient compression and streaming, and touchscreens on indoor monitors or mobile apps for two-way video calls. IP cameras provide wide-angle views and motion detection, while H.264 offers broad compatibility for standard-definition to HD streams, and H.265 reduces bandwidth usage by up to 50% for higher resolutions without quality loss. Touchscreens, often 7-inch capacitive displays, support intuitive interfaces for viewing feeds and controlling door releases.^[67]^[68]^[69] The primary advantages of video integration lie in bolstered security for door entry scenarios, where users can visually confirm visitors to prevent unauthorized access, and the ability to conduct remote monitoring without deploying a separate CCTV infrastructure. This integration deters potential intruders through visible deterrence and records interactions for evidentiary purposes, enhancing overall property safety. For residential settings, it streamlines package deliveries and visitor management by allowing remote interaction via smartphones.^[70]^[71]^[72] Technically, video streams in intercom systems demand bandwidth of 1-5 Mbps per stream for HD quality, depending on resolution and codec—H.264 HD streams typically require 2-4 Mbps, while H.265 optimizes to 1-2 Mbps for similar clarity. Night vision integration, often via infrared illuminators, ensures functionality in low-light conditions, extending visibility up to 10-20 meters without ambient light. Audio-video synchronization is achieved through timestamping in IP packets, maintaining lip-sync within 100 milliseconds to mimic in-person exchanges.^[73]^[74]^[66] Representative examples include the Ring Video Doorbell Wired, a residential system featuring a 1080p HD camera with night vision and two-way audio over Wi-Fi, enabling remote viewing and talk via app integration. Similarly, Aiphone's JV Series provides a wired video door entry solution for homes, with a color camera, picture recording, and compatibility for up to two indoor stations, emphasizing reliable visual verification for single-family or small multi-unit residences.^[75]^[76]

Network-Based Systems

Network-based intercom systems utilize IP and Ethernet infrastructure to transmit audio communication as data packets, enabling flexible deployment over local area networks (LANs) or wide area networks (WANs). The core architecture relies on Session Initiation Protocol (SIP) and Voice over Internet Protocol (VoIP) for signaling and routing calls between endpoints, allowing devices such as door stations and indoor units to initiate, maintain, and terminate sessions dynamically.^[77] Power over Ethernet (PoE) simplifies installation by delivering both power and data through a single Category 5 or higher Ethernet cable, eliminating the need for separate power supplies and reducing cabling complexity.^[77] These systems offer significant advantages in scalability, allowing deployment across multiple buildings or sites without extensive rewiring, as additional endpoints can be added via standard network switches.^[77] Remote management is facilitated through cloud-based platforms, enabling administrators to configure devices, monitor status, and update firmware from anywhere with internet access.^[78] Integration with Internet of Things (IoT) devices, such as smart locks and sensors, enhances functionality by allowing intercoms to trigger automated actions like unlocking doors or activating alarms based on network events.^[77] Technical optimizations ensure reliable performance, with latency typically kept below 50 milliseconds to support real-time, hands-free conversations comparable to traditional systems.^[79] VLAN segmentation provides security by isolating intercom traffic on dedicated virtual networks, preventing unauthorized access and reducing the risk of broadcast storms or eavesdropping on shared infrastructure.^[77] This approach evolved from earlier digital intercoms by leveraging packet-switched networking for greater efficiency. Prominent examples include 2N's IP intercom series, such as the 2N IP Verso, which supports SIP-based multi-site deployments in enterprises, offering PoE-powered modular units for scalable access control across office complexes.^[80] Similarly, Comelit's ViP system uses IP architecture with SIP/VoIP for multi-tenant environments, enabling remote cloud management and IoT integrations like app-based door release in distributed properties.^[81]

Applications and Installations

Permanent Installations

Permanent installations of intercom systems involve fixed infrastructure embedded within building structures to facilitate long-term communication in environments such as offices, apartments, and commercial facilities. These setups typically feature wall-embedded wiring that routes audio and power signals through conduits integrated into walls, floors, and ceilings, ensuring seamless connectivity without visible cabling. Design considerations include zoning for specific floors or rooms, where subsystems are divided to allow targeted communication, such as resident-to-concierge links in high-rises. One key advantage of permanent installations is their reliability, as hardwired connections reduce susceptibility to interference compared to wireless alternatives, providing consistent performance in dense urban settings. They also offer aesthetic integration, with flush-mounted panels and speakers that blend into architectural elements, enhancing the building's visual appeal. Additionally, these systems comply with building codes like the Americans with Disabilities Act (ADA), incorporating features such as tactile buttons and visual indicators for accessibility in public and residential spaces.^[82] Challenges in permanent installations include high upfront costs due to the labor-intensive process of embedding wiring during construction or retrofitting, often ranging from $5,000 to $25,000 for multi-story buildings depending on size.^[83] Maintenance for cabling is another hurdle, requiring periodic inspections for corrosion or damage in concealed areas, which can disrupt service if not addressed proactively. Examples of permanent installations include multi-tenant apartment systems, where central master stations in lobbies connect to individual unit substations via zoned wiring, enabling secure entry control and emergency paging across the property. In office complexes, similar setups integrate with access control systems, using embedded cabling to link conference rooms and reception areas for efficient internal coordination. Components such as wall-mounted speakers and keypads from standard system inventories are commonly employed to ensure compatibility.

Portable and Temporary Setups

Portable and temporary intercom setups are designed for mobility and rapid deployment, featuring battery-powered units that enable operation without access to fixed power sources. These systems typically incorporate modular belt packs, which are lightweight, wearable devices that allow team members to communicate hands-free while moving freely. For instance, many belt packs utilize rechargeable NiMH or standard AA batteries, providing up to 16 hours of continuous use to support extended events. Quick-connect cables or wireless pairing mechanisms facilitate swift assembly, often requiring minimal technical expertise for setup in under 30 minutes.^[84] The primary advantages of these setups lie in their adaptability to dynamic environments such as live events and theaters, where configurations can be reconfigured on-site without necessitating structural modifications to venues. This portability eliminates the need for permanent infrastructure, reducing setup costs and time compared to wired alternatives, and allows for seamless integration into temporary spaces like stages or outdoor locations. In theatrical productions, for example, these systems support coordinated cueing among crew members across large areas without disrupting the performance space.^[85]^[86] Despite their flexibility, portable intercoms face challenges including range limitations, often restricted to 100-500 meters in open spaces depending on the wireless technology employed, which can hinder coverage in expansive or obstructed venues. Signal interference from nearby RF sources, such as other wireless devices or environmental factors like metal structures, poses another issue in dynamic settings, potentially causing audio dropouts or reduced clarity during high-movement activities. To mitigate these, systems may incorporate frequency-hopping or DECT-based protocols for improved reliability in crowded event scenarios.^[87]^[88] Practical examples include wireless kits tailored for film crews, such as the Hollyland Solidcom series, which provides full-duplex communication for directors and operators on location shoots, enabling real-time coordination without cabling. Similarly, conference AV setups often utilize compact systems like the Saramonic WiTalk-WT5D, supporting up to five users for panel discussions or hybrid events with easy battery-powered deployment. These configurations highlight the role of portable intercoms in professional production environments requiring quick teardown after use.^[89]^[86]

References

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Intercom | Company Overview & News - Forbes
Intercom ; Industry: AI customer service ; Founded: 2011 ; Headquarters: San Francisco, California ; Country/Territory: United States ; CEO: Eoghan McCabe.
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About | Intercom
Intercom is a fundamentally new way for internet businesses to communicate with customers, personally. We're the first to bring messaging products for sales ...
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What is Intercom? | Intercom Help
The Intercom Customer Service Suite scales with teams across diverse industries—from highly regulated environments like Finance and Fintech to dynamic sectors ...What Does Intercom Offer? · Helpdesk · Plus Proactive Support...
[4]
Intercom System 101 - What is,Function,Types
May 14, 2025 · An intercom system (short for Intercommunication System) is a two-way voice communication system used in buildings or groups of buildings.
[5]
Intercom Systems: All of Your Questions Answered - ButterflyMX
May 1, 2025 · An intercom system is an electronic device that enables two-way communication between people. It also allows people in a building to grant property access to ...Components of an intercom... · The 9 types of intercom systems
[6]
https://www.syncoaudio.com/blogs/news/what-is-intercom-used-for-uses-explained
[7]
What is intercom used for: 6 common uses explained - SYNCO
Jan 1, 2025 · An intercom system is a device that allows two-way communication between individuals. They are widely used in various environments to provide communication and ...
[8]
What is Intercom? Unveiling the Power of Communication - BAS-IP
May 14, 2023 · An intercom system works by transmitting audio or video signals over a wired or wireless network. The specifics depend on the type of intercom ...
[9]
What is the difference between a PA system, a Public Address ...
A PA or Public Address System is typically a local one-way speaker system intended to deliver audio announcements to a facility. An Intercom System is typically ...Missing: telephone | Show results with:telephone
[10]
What is the difference between Telephone and Intercom? - YUMPU
Mar 11, 2015 · Telephone uses electricity for external/internal communication. Intercom supplements private branch exchange, operates without an exchange, and ...
[11]
What is the working principle of intercom system?
May 23, 2025 · They operate on basic principles of connectivity, where physical cables serve as conduits for transmitting audio signals.
[12]
How Does Intercom Work | A Simple Guide to Systems & Uses
At its core, an intercom system operates on the idea of capturing a voice, sending it through a channel, and playing it back on the other end. Here is how the ...
[13]
Intercom Phone System vs. IP Intercom: A Modern Comparison
Apr 22, 2023 · An IP intercom system uses internet protocol (IP) technology for communication, allowing for enhanced audio quality, easy scalability, simplified installation, ...
[14]
Intercom - Etymology, Origin & Meaning
"Intercom," from 1911 as linked telephone systems, colloquially shortened in 1937, means a radio or telephone intercommunication system.
[15]
https://products.rtsintercoms.com/binary/Handbook%20of%20Intercom%20Systems%20Engineering.pdf
[16]
None
Below is a merged summary of key intercom terminology from the "Handbook of Intercom Systems Engineering," consolidating all information from the provided segments into a single, comprehensive response. To maximize detail and clarity, I’ve organized the information into a table in CSV format, which includes definitions, examples, page references, and additional notes from all segments. Following the table, I’ll provide a concise narrative summary and list all useful URLs mentioned across the segments.
[17]
[PDF] A Comprehensive Guide to Clear-Com Analog and Digital Partyline ...
A Clear-Com analog partyline intercom is a closed-circuit intercom system that consistently provides high-clarity communication in both high-noise and low-noise ...
[18]
The History of the Apartment Intercom System | ButterflyMX
Apr 4, 2025 · The first telephone-based intercom was patented in 1894, using a buzzer to alert residents. Apartment intercoms evolved to include earpieces ...
[19]
Mr. Watson, Come Here: A History of the Development ... - Clear-Com
Jul 4, 2017 · One unique intercom system for use in noisy environments was made in England in the 1930's. Called the Loudaphone, it was installed in places ...
[20]
Can You Hear Me Now?: A History of the Development of the ...
Jul 26, 2017 · ... intercom systems started to be used in live theater. There were standard handset-based phone instruments located backstage, in offices, out ...
[21]
The Evolution of Intercoms: How Communication Tech Transformed ...
Sep 10, 2024 · The emergence of digital integrated circuits during the 1970s was another driving force in intercom system makeovers, with companies beginning ...
[22]
The History of Carbon Microphones and Artifacts from the Shure ...
Apr 29, 2020 · The history of carbon microphones goes back to the 19th century. An Englishman named David Edward Hughes fabricated one of the first carbon mics in the 1870s.
[23]
[PDF] A Saga of RTS Systems, The Intercom Company - Best Audio
Oct 1, 2014 · Because we planned on using microphone cable, we made the male and female connectors opposite to the cables that actually connected microphones, ...
[24]
Our Story - Clear-Com 50th Anniversary
Jan 19, 2018 · In the early 1980s, Clear-Com introduced its first digital intercom system, Matrix Plus, to address the needs of more demanding television ...
[25]
The Evolution of Audio Intercom Systems in Modern Broadcast and ...
Nov 25, 2024 · Dave Mackinnon explains the importance of intercom systems for modern broadcast and live event purposes, as well as the evolution of comms.Missing: analog | Show results with:analog<|control11|><|separator|>
[26]
Intercoms: A History of Distance | AVNetwork
Sep 15, 2022 · The earliest intercom uses date back to the late 1960s and early 1970s, when concerts became too loud to allow for waving pieces of paper or shouting from the ...
[27]
Evolution of Intercom Technology in TV Broadcasting - Samim Group
Oct 15, 2024 · About Samim IP-based Intercom System · 1. Early Days · 2. Analog Intercom Systems (1960s-1980s) · 3. Digital Revolution (1990s) · 4. Networked ...
[28]
Complete guide to smart door entry intercom security systems - Pelco
Base stations house the hardware for intercom door entry systems, which includes an intercom buzzer, a directory of occupants, a microphone and an intercom ...
[29]
Complete Buyer's Guide to Door Entry Intercom Systems - Avigilon
May 24, 2023 · Intercom systems allow two-way communication between separate areas. They have a variety of uses, from providing basic interconnectivity in ...Types Of Intercom Entry... · Wireless Intercom System · Networked Intercom System
[30]
[PDF] EHX Configuration Software - Clear-Com
Online and offline configuration changes. • Non-intrusive configuration downloads allow system changes without disruption. • Client/Server operation enables ...
[31]
AZedit | RTS Intercoms
It gives you the ability to manage multiple intercom systems, assign and reassign users to different ports, as well as dynamically add intercom hardware to your ...
[32]
Digital Matrix Intercom Systems
RTS matrices are the standard for reliable,mission-critical communications in broadcast, aerospace, industrial and entertainment applications.
[33]
[PDF] AZedit Software User Manual - RTS Products
Dec 3, 2011 · Intercom system configuration has never been easier with the advent of Bosch's AZedit Intercom System software. AZedit is a. Windows-based ...
[34]
Keypanels | RTS Intercoms
The alphanumeric call waiting window is used for scrollable access to all ports, PLs, ISOs, IFBs, etc. and to check and make key assignments.
[35]
SymMX API: The secure interface to the world of Commend ...
Mar 24, 2023 · Our API allows not only Intercom Stations, but also Symphony Modules to be easily controlled directly by external systems.Missing: professional | Show results with:professional
[36]
Agent-IC Mobile App - Clear-Com
Agent-IC mobile applications provides you with a cost-effective and fast-to-deploy solution that complements traditional intercom systems.
[37]
Choosing the Right Wireless Intercom System: 2-wire & 4-wire ...
May 14, 2018 · In intercom channels, there are four wires (two paths). 4-wire systems can be 4-wire balanced or 4-wire unbalanced. The 4-wire circuit gets its ...
[38]
Demystify Audio: Wireless Intercom Systems - TC Furlong
Jun 18, 2020 · For instance, Radio Active Designs uses VHF frequenices (174-216 MHz) for uplink, and UHF frequencies (470-608 MHz) for downlink. Learn more ...<|control11|><|separator|>
[39]
Choosing the Right Wireless Intercom System: System Coverage ...
May 21, 2018 · Typical distances are between approximately 50 m (160 ft) and 150 m (485 ft), depending on the environment. As the antenna requirements for an ...
[40]
Wireless Intercom Systems
Available wireless intercom systems include ROAMEO (DECT), UHF (with digital encryption), and TT-16 (VHF for on-air talent).
[41]
A complete guide to wireless stage intercom - SYNCO
Jun 21, 2025 · Wireless intercom systems give stage crews freedom to move around without being limited by cables. This is especially useful for large stages ...
[42]
https://www.intercomsonline.com/fcc-license-for-two-way-radios
[43]
https://www.crfs.com/blog/radio-frequency-interference-how-to-find-it-and-fix-it
[44]
Radio frequency interference (how to find it and fix it) - CRFS
Find and fix RFI faster with real-time spectrum monitoring, wideband low-noise sensors, geolocation, and alerts, cutting detection and repair time.
[45]
Tech Spotlight: Radio Active Designs Frees Up Bandwidth In A ...
Jun 2, 2025 · The UV-1G frees up UHF bandwidth by operating in the VHF range, using a 25 kHz bandwidth, and is 10x more spectrally efficient than FM.
[46]
Digital Enhanced Cordless Telecommunications (DECT) - ETSI
DECT is the second most successful ETSI standard after GSM. We have provided a high number of DECT devices manufactured from the beginning reaches 820 ...
[47]
[PDF] Digital Enhanced Cordless Telecommunications and Wireless ...
What is DECT? How is it allocated by the ETSI. How has the FCC regulated DECT. Why manufacturers choose the DECT band for wireless intercoms.
[48]
[PDF] EN 300 175-1 - V2.8.5 - Digital Enhanced Cordless ... - ETSI
DECT Standard Cipher #2 (DSC2): algorithm used for data encryption in DECT ... GHz are specified in various ETSI DECT standards. The specific variants for ...Missing: intercom | Show results with:intercom
[49]
Network intercoms | Axis Communications
Network intercoms combine video surveillance, two-way communication, and remote entry control in a single device for secure, hassle-free physical access to ...Audio intercoms · Video intercoms · Answering units · Safety intercoms
[50]
[PDF] bolero wireless intercom - Riedel Communications
Next generation, digital, license free 1.9GHz DECT band. Riedel-exclusive ADR receiver technology overcomes multipath issues. Modern high-clarity voice codec ...
[51]
[PDF] Vingtor-Stentofon Phontech Maritime & Energy Catalog - Zenitel
IP DECT base stations connect directly to the exchange over IP, providing a very cost-efficient solution for deploying a wireless network onboard. The DECT ...Missing: aviation | Show results with:aviation
[52]
What is Push-to-Talk over Cellular? Hytera US
PoC Features and Benefits · Flexible Single-Site, Multi-Site, and Nationwide Coverage · No Radio Infrastructure or FCC Frequencies Required · Rapid Deployments.<|control11|><|separator|>
[53]
What is broadband push to talk? - Motorola Solutions EMEA
Push-to-talk over cellular (PoC or PTToC) is a solution that allows people to instantly communicate with other users at the push of a button on their internet- ...
[54]
https://www.motorolasolutions.com/en_xu/solutions/what-is-broadband-push-to-talk.html
[55]
Push-To-Talk over Cellular [PoC] Market Share & Forecast, 2032
Integrating advanced technologies such as 5G further enhances cellular network devices' performance, providing low-latency communication essential for ...
[56]
https://www.fortunebusinessinsights.com/push-to-talk-over-cellular-poc-market-108945
[57]
Push to Talk over Cellular - AIRACOM (PoC) LTE Two Way Radios
Push to talk over cellular (PoC) radios provide near global coverage over any 2G, 3G, 4G LTE, 5G and WiFi network. Airacom is a PoC manufacturer.
[58]
Understanding Push-to-talk over Cellular: Key benefits and use cases
Sep 11, 2024 · It offers a seamless, flexible, and scalable approach to communication, transforming how industries stay connected.
[59]
Push to Talk over Cellular Solution Advantages & Disadvantages
Aug 16, 2024 · Push to Talk Over Cellular (PoC) improves communication by providing broader information, real-time communication, and advanced features.
[60]
Two-Way Radios vs. Push-to-Talk Over Cellular (POC): What's the ...
Limitations: · Monthly service fees: Typically, a subscription-based model. · Dependent on network availability: Poor cellular coverage = poor performance.
[61]
PoC System for the Large Enterprise - Hytera US
The HORIZON PoC platform supports end-to-end digital encryption for secure and private communications. Digital encryption provides the maximum level of security ...
[62]
Unlocking Efficiency: The Benefits of Push-to-Talk over Cellular
May 2, 2025 · Unlike traditional radio networks, PoC removes the limitations of repeater and base station ranges, offering extensive coverage. Businesses ...
[63]
Hardware | Devices (Zello Push-to-Talk App Accessories)
Zello is compatible with most current smartphones and tablets. Looking for something loud and durable? Check out our favorite rugged devices below.
[64]
https://zello.com/hardware/hardware-devices/
[65]
Complete Buyer's Guide to Video Door Intercom Systems - Avigilon
Further considerations such as night vision and low-light recording settings are worth looking into if the system is intended to be used at all hours.
[66]
2N IP Force 2.0: Durable video intercom with 5MPx camera
Jul 25, 2025 · Discover the 2N IP Force 2.0 – a durable video intercom with a 5MPx camera. Featuring QR code access, enhanced audio, and more!Missing: components | Show results with:components
[67]
JP Series Video Intercom - Aiphone
Aiphone JP Series video intercom provides secure video communication and access control for residential and commercial properties.JP-4MED · Banner · JPS-4AEDV · JP-4HD
[68]
Wired PoE IP Video Intercom Kit Door Phone/Bell 7-inch Colorful ...
Hik video intercom system include indoor monitor and outdoor video doorbell camera, indoor monitor is equipped with 7 inch colorful touch screen.
[69]
What Are The Benefits Of A Video Intercom System? - PSA Products
Sep 20, 2023 · Video intercoms enhance security with real-time monitoring, improve communication with visual context, and offer convenience through remote ...
[70]
Video Door Intercoms: Enhancing Home Security and Convenience
Oct 9, 2023 · One of the most significant advantages of video door intercoms is the ability to remotely view and interact with visitors at your doorstep.
[71]
What is the bandwidth requirement for a video intercom system? - Blog
Jun 20, 2025 · An SD video intercom system might need around 500 kbps to 1 Mbps of bandwidth. This is because the lower number of pixels means less data ...
[72]
Empowering Video Intercom System for Apartments - BAS-IP
Apr 11, 2023 · Night Vision. Night vision is an essential feature to consider when choosing an intercom video system. It enables you to clearly see visitors, ...
[73]
https://www.mzelectr.com/blog/what-is-the-bandwidth-requirement-for-a-video-intercom-system-299195.html
[74]
Intercom System for Residential Properties - aiphone.net
The JV Series is a basic 1:2 video door entry system with a picture recording function, accommodating both wet and dry contact methods for door lock release.
[75]
None
### Summary of IP-Based Intercom System Architecture and Features
[76]
2N: Global Leader in IP Intercoms and Access Control
Choose from 2N's range of market leading IP technology to meet the needs of every customer and create the perfect IP door access control system for any project ...2N IP Style · 2N IP One · 2N EasyGate IP · 2N IP ForceMissing: enterprises | Show results with:enterprises
[77]
What is Good Latency in Networking? - Obkio
Rating 4.9 (161) Aug 13, 2024 · 50ms to 100ms: Acceptable latency for some applications, though users may start to notice a delay, especially in real-time communications and ...Missing: intercom | Show results with:intercom
[78]
2N IP Verso 2.0
The second generation of the world's best-selling IP intercom boasts a wide-angle, full-HD camera and a new ARTPEC-7 processor that powers advanced features ...
[79]
Intercom - Comelit Group
Comelit intercom systems are designed to streamline communication and access control for residents, providing unparalleled peace of mind.Missing: multi- | Show results with:multi-
[80]
https://www.2n.com/en-US/products/intercoms/2n-ip-verso-2/
[81]
Live Performance & Events - Clear-Com
Our iconic Encore Analog Partyline system delivers basic, reliable and proven intercom for production houses, while the HelixNet Digital Partyline system is ...
[82]
The Best Wireless Intercom System for Production and Live Events
Mar 12, 2024 · WiTalk-WT5D represents a state-of-the-art wireless intercom system exclusively designed for professional production teams.
[83]
Using Wireless Intercom Systems in Different Scenarios - Saramonic
Jun 9, 2025 · Instantly upgrade team comms! Explore wireless intercoms for clear, reliable audio in broadcasting, security & industry.
[84]
4 Reasons NOT to Use Wireless Intercom System for Buildings
May 8, 2023 · Reliability, Wireless systems are prone to signal interference and dropped connections. ; Security, Wireless systems can be vulnerable to hacking ...
[85]
19 Best Wireless Intercom Systems in 2024 - Hollyland
Jun 26, 2025 · This article shows you the 19 best wireless intercom systems. The list includes top-notch wireless intercoms for filmmaking, home, and office use.