Intercom
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An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building, small collection of buildings or portably within a small coverage area, which functions independently of the
Intercoms are used on a wide variety of properties; from houses that only require one connection between a resident and the property's entrance to multi-unit apartments that require intercom hardware to be installed in every individual apartment.
Permanent systems
Traditional intercoms and public address systems are composed entirely of analogue electronics components but many new features and interfacing options can be accomplished with new intercom systems based on digital connections. Video signals can be carried as well as voice. Digital intercom stations can be connected using Cat 5 cable and can even use existing computer networks as a means of interfacing distant parties. Intercom cameras can be used in modern offices and hotels.
Many schools and office buildings now use audio / video systems to identify visitors trying to gain access to a locked building and can be interfaced with the building's access control system.
Besides fixed locations, intercom systems are used on many types of vehicles including trains, watercraft, aircraft and armoured fighting vehicles.
Portable systems
Portable intercoms are commonly used by
Portable intercoms are also used for motorcycle communication, for example between motorcyclist and passenger, bike-to-bike communication or communication within a pack of riders. Intercom mounting systems can be attached to most motorcycle helmets.[2] Several different types of technologies can be used, including various types of citizens band radio like for example PMR446, Bluetooth, or dynamic mesh communication (DMC) which is a mesh based intercom system developed for motorcycle communication.[3]
Basic intercom system terms
Intercom installers, suppliers, and manufacturers often use the following terms to refer to intercom components.
- Master station or base station: These units control the whole system. Master stations initiate calls to substations and can be configured to make announcements that are transmitted over the entire intercom system.
- Substation: Units that initiate calls with a master station, but are not capable of initiating calls with any other stations. Substations are also known as slave units.
- Door station: Like substations, door stations are only capable of initiating a call to a master station. They are typically weather-proof.
- Intercom station: A full-featured remote unit that is capable of initiating and receiving party-line conversation, individual conversations, and signalling. May be rack-mounted, wall-mounted or portable.
- Wall mount station: Fixed-position intercom station with built-in loudspeaker. May have flush-mounted microphone, hand-held push to talkmicrophone or telephone-style handset.
- Belt pack: Portable intercom station worn on the belt such as an earpieceworn by talent.
- Handset: Permanent or portable telephone-style connection to an intercom station. Holds both an earpiece and a push to talkmicrophone.
- Headset: Portable intercom connection from a belt pack to one or both ears via headphones with integrated microphone on a boom arm. Connects to a belt pack.
- Paging signal: An audible and/or visual alert at an intercom station, indicating that someone at another station wants to initiate a conversation.
- Power supply: Used to feed power to all units. Often incorporated into the design of the base station.
- Telephonic: Intercom systems that utilize a transmitter (talk) and receiver (listen) to communicate, similar to standard telephone systems.
- Amplified: Intercom systems that utilize a single speaker to transmit and receive communications.
- Amplifier: An intercom system's main or central component, responsible for switching or connecting communication paths between master and substations. In addition, amplifiers distribute or switch power to auxiliary connected devices, such as door strikes, to allow entry.
Wiring intercoms
While every intercom product line is different, most analogue intercom systems have much in common. Voice signals of about a volt or two are carried atop a direct current power rail of 12, 30 or 48 volts which uses a pair of conductors. Signal light indications between stations can be accomplished through the use of additional conductors or can be carried on the main voice pair via tone frequencies sent above or below the speech frequency range. Multiple channels of simultaneous conversations can be carried over additional conductors within a cable or by frequency- or time-division multiplexing in the analogue domain. Multiple channels can easily be carried by packet-switched digital intercom signals.
Portable intercoms are connected primarily using common shielded, twisted pair microphone cabling terminated with 3-pin XLR connectors. Building and vehicle intercoms are connected in a similar manner with shielded cabling often containing more than one twisted pair.
Digital intercoms use Category 5 cable and relay information back and forth in data packets using the Internet protocol suite.
Two-wire broadcast intercoms
Intercom systems are widely used in TV stations and
Four-wire broadcast intercoms
In the mid-90s four-wire technology started gaining more prominence due to the technology getting cheaper and smaller.
Wireless intercoms
For installations where it is not desirable or possible to run wires to support an intercom system, wireless intercom systems are available. There are two major benefits of a wireless intercom system over the traditional wired intercom. The first is that installation is much easier since no wires have to be run between intercom units. The second is that you can easily move the units at any time. With that convenience and ease of installation comes a risk of interference from other wireless and electrical devices. Nearby wireless devices such as cordless telephones, wireless data networks, and remote audio speakers, as well as structural features in your building, can all interfere. Electrical devices such as motors, lighting fixtures and transformers can cause noise. There may be concerns about privacy since conversations may be picked up on a scanner, baby monitor, cordless phone, or a similar device on the same frequency. Encrypted wireless intercoms can reduce or eliminate privacy risks, while placement, installation, construction, grounding and shielding methods can reduce or eliminate the detrimental effects of external interference. The United States and Canada have several frequency ranges for wireless intercom systems and other wireless products. They are 49 MHz, FM band (200–270 kHz), 494–608 MHz, 900 MHz, 2.4 GHz, 5.8 GHz, and MURS (150 MHz). IP Intercoms are now appearing that connect a Master to an IP Substation elsewhere on the Internet, via an Ethernet port. Wireless intercoms can also run over a mesh network that allows near-instant communication throughout a house.
Telephone intercoms
Some telephones include intercom functions that enable paging and conversation between instruments of similar make and model. Examples include Panasonic model KX-TS3282W(/B), AT&T models 945 and 974, and TMC model ET4300.
A single device can add intercom functionality to multiple standard telephones on a common phone line, even of different makes and models. Installation effort is minimal, and is not vulnerable to the radio interference and security issues of wireless systems. The Add-A-Com Whole House Intercom for Standard Telephone Systems is such a device. Intercom paging is accomplished by sounding a distinctive ring from all telephones after any phone is taken briefly off hook. After paging, any number of phones may converse. The device temporarily disconnects the external phone line during intercom use, and reconnects when all phones are again on hook. During intercom use, an external call’s ringing signal can be heard in the earpiece.
Many
See also
- Courtesy telephone, a telephone for relaying messages to a specific person after being notified via a public address system, or for customers to seek information
- Door phone, electronic device for communication with someone outside a building
- Video door-phone, audiovisual communication device enabling visual identification of a visitor
- Public address system, a system for distributing the voice of an announcer over a large area
- Speaking tube, an air pipe through which speech can be transmitted over an extended distance
- Tank phone, similar device used in Tanks and Armoured vehicles
- Telemetry, remote collection of data for monitoring
- Voice chat in online gaming
References
- ^ a b c Lange, Kim (2017-02-08). "Intercom systems — how do they work?". Medium. Retrieved 2022-07-27.
- ^ Are Bluetooth Motorcycle Helmets Safe? (Safety & Standards) – Moto1
- ^ What Are the Benefits of Using Mesh vs. Bluetooth Communication?