BACnet is a communication protocol for building automation and control (BAC) networks that use the ASHRAE , ANSI , and ISO 16484-5 standards protocol.
75-457: BACnet was designed to allow communication of building automation and control systems for applications such as heating, ventilating, and air-conditioning control ( HVAC ), lighting control, access control, and fire detection systems and their associated equipment. The BACnet protocol provides mechanisms for computerized building automation devices to exchange information, regardless of the particular building service they perform. The development of
150-471: A 10 Mbit/s Ethernet in a busy office on slow processors, ARCNET ultimately gave way to Ethernet as improved processor speeds reduced the impact of collisions on overall throughput, and Ethernet costs dropped. In the early 1980s ARCNET was much cheaper than Ethernet, in particular for PCs. For example, in 1985 SMC sold ARCNET cards for around US$ 300 whilst an Ungermann-Bass Ethernet card plus transceiver could cost US$ 500 . Another significant difference
225-454: A passivhaus design intended to consume no net energy whatsoever will typically require a BAS to manage heat capture , shading and venting, and scheduling device use. Building management systems are most commonly implemented in large projects with extensive mechanical, HVAC, and electrical systems. Systems linked to a BMS typically represent 40% of a building's energy usage; if lighting is included, this number approaches to 70%. BMS systems are
300-426: A buildings climate within a specified range, provide light to rooms based on occupancy, monitor performance and device failures, and provide malfunction alarms to building maintenance staff. A BAS works to reduce building energy and maintenance costs compared to a non-controlled building. Most commercial, institutional, and industrial buildings built after 2000 include a BAS, whilst older buildings may be retrofitted with
375-455: A critical component to managing energy demand. Improperly configured BMS systems are believed to account for 20% of building energy usage, or approximately 8% of total energy usage in the United States. In addition to controlling the building's internal environment, BMS systems are sometimes linked to access control (turnstiles and access doors controlling who is allowed access and egress to
450-423: A frequency of pulses accordingly. Controllers are essentially small, purpose-built computers with input and output capabilities. These controllers come in a range of sizes and capabilities to control devices commonly found in buildings, and to control sub-networks of controllers. Inputs allow a controller to read temperature, humidity, pressure, current flow, air flow, and other essential factors. The outputs allow
525-612: A larger failure. Some sites are programmed so that critical alarms are automatically re-sent at varying intervals. For example, a repeating critical alarm (of an uninterruptible power supply in 'bypass') might resound at 10 minutes, 30 minutes, and every 2 to 4 hours thereafter until the alarms are resolved. Security systems can be interlocked to a building automation system. If occupancy sensors are present, they can also be used as burglar alarms. Because security systems are often deliberately sabotaged, at least some detectors or cameras should have battery backup and wireless connectivity and
600-450: A leak), or when excess methane is detected in the building's air supply. Most building automation networks consist of a primary and secondary bus which connect high-level controllers (generally specialized for building automation, but may be generic programmable logic controllers ) with lower-level controllers, input/output devices and a user interface (also known as a human interface device). ASHRAE 's open protocol BACnet or
675-399: A load upon command. An example would be to turn on the parking lot lights when a photocell indicates it is dark outside. Another example would be to open a valve by allowing 24VDC/AC to pass through the output powering the valve. Analog outputs could also be pulse type outputs emitting a frequency of pulses over a given period of time. An example is an energy meter calculating kWh and emitting
750-616: A new BAS. A building controlled by a BAS is often referred to as an intelligent building, a "smart building", or (if a residence) a " smart home ". Commercial and industrial buildings have historically relied on robust proven protocols (like BACnet ) while proprietary protocols (like X-10 ) were used in homes. With the advent of wireless sensor networks and the Internet of Things, an increasing number of smart buildings are resorting to using low-power wireless communication technologies such as Zigbee, Bluetooth Low Energy and LoRa to interconnect
825-504: A number of data link and physical layers, including ARCNET , Ethernet , BACnet/IP, BACnet/IPv6, BACnet/MSTP, point-to-point over RS-232 , multidrop serial bus with token passing over RS-485 , Zigbee , and LonTalk . ANSI/ASHRAE 135-2016 specifies 60 standard object types: BACnet Testing Laboratories ("BTL") was established by BACnet International to test products to BACnet standards and support compliance testing and interoperability testing activities and consists of BTL Manager and
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#1732851544783900-449: A number of services that are used to communicate between building devices. The protocol services include Who-Is, I-Am, Who-Has, I-Have, which are used for Device and Object discovery. Services such as Read-Property and Write-Property are used for data sharing. As of ANSI/ASHRAE 135-2016, the BACnet protocol defines 60 object types that are acted upon by the services. The BACnet protocol defines
975-638: A potentially hazardous or costly situation if no one who can solve the problem is notified. Notification can be through a computer (email or text message), pager , cellular phone voice call, audible alarm, or all of these. For insurance and liability purposes all systems keep logs of who was notified, when and how. Alarms may immediately notify someone or only notify when alarms build to some threshold of seriousness or urgency. At sites with several buildings, momentary power failures can cause hundreds or thousands of alarms from equipment that has shut down – these should be suppressed and recognized as symptoms of
1050-399: A predictable maximum time; thus it is deterministic . This made ARCNET an ideal real-time networking system, which explains its use in the embedded systems and process control markets. Token Ring has similar qualities, but is much more expensive to implement than ARCNET. In spite of ARCNET's deterministic operation and historic suitability for real-time environments such as process control,
1125-777: A response to the dominance of International Business Machines (IBM) and its Systems Network Architecture (SNA). In 1979, the Open Systems Interconnection Reference Model ( OSI model ) was published. Then, in 1980, Digital, Intel and Xerox (the DIX consortium) published an open standard for Ethernet that was soon adopted as the basis of standardization by the IEEE and the ISO. IBM responded by proposing Token Ring as an alternative to Ethernet but kept such tight control over standardization that competitors were wary of using it. ARCNET
1200-491: A simple, small, unpowered box with four ports, wired together with nothing more than four discrete resistors, so the disadvantage was not significant. This disadvantage can also be seen as an advantage, often the cost of a 4 port ARCNET passive hub was less than cost of the 4 BNC Tee connectors and 2 terminators that thin Ethernet requires to connect 4 computers, and unlike BNC Tee connectors that could sometimes be hard to obtain in
1275-421: A single "token" message is passed around the network from machine to machine, and no peer is allowed to use the bus unless it has the token. If a particular peer wishes to send a message, it waits to receive the token, sends its message, and then passes the token on to the next station. Because ARCNET is implemented as a distributed star, the token cannot be passed machine to machine around a ring. Instead, each node
1350-405: A single computer with dumb terminals. When the number of users outgrew the capacity of the original computer, additional 'compute' resource computers could be attached via ARCNET, running the same applications and accessing the same data. If more storage was needed, additional disk resource computers could also be attached. This incremental approach broke new ground and by the end of the 1970s (before
1425-499: A special connector. This special connector, called a terminator, is nothing more than a BNC connector with a 93 ohm resistor in it. Thin Ethernet also requires nearly identical terminators at the 2 terminal ends, the only difference being Ethernet uses a 50 ohm resistor. To reduce costs, while still allowing coverage over a wide area, a common practice was to use one or more interconnected active hubs, each of which provided coverage for nodes no more than 60 m (200 ft) away. Cable
1500-413: A stand-alone AC system) into a central building automation system. Terminal unit controllers usually are suited for control of lighting and/or simpler devices such as a package rooftop unit, heat pump, VAV box, fan coil, etc. The installer typically selects one of the available pre-programmed personalities best suited to the device to be controlled, and does not have to create new control logic. Occupancy
1575-487: A variable measurement. Examples are temperature , humidity and pressure sensors which could be thermistor , 4–20 mA , 0–10 volt or platinum resistance thermometer (resistance temperature detector), or wireless sensors . A digital input indicates a device is on or off. Some examples of digital inputs would be a door contact switch, a current switch, an air flow switch , or a voltage-free relay contact (dry contact). Digital inputs could also be pulse inputs counting
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#17328515447831650-509: Is a subset of building automation and with a similar purpose; it is the consolidation of one or more systems under centralized control, though in this case in one room. The most common example of room automation is corporate boardroom, presentation suites, and lecture halls, where the operation of the large number of devices that define the room function (such as videoconferencing equipment, video projectors , lighting control systems , public address systems etc.) would make manual operation of
1725-489: Is assigned an 8 bit address (usually via DIP switches), and when a new node joins the network a "reconfig" occurs, wherein each node learns the address of the node immediately above it. The token is then passed directly from one node to the next. Historically, each approach had its advantages: ARCNET added a small delay on an inactive network as a sending station waited to receive the token, but Ethernet's performance degraded drastically if too many peers attempted to broadcast at
1800-479: Is good enough to run ARCNET. Some ARCNET twisted-pair products supported cable runs over 2,000 ft (610 m) on standard Cat-3 cable, far beyond anything Ethernet could do on any kind of copper cable. In the early 1990s, Thomas-Conrad Corporation developed a 100 Mbit/s topology called TCNS based on the ARCNET protocol, which also supported RG-62, twisted-pair, and fiber optic media. TCNS enjoyed some success until
1875-450: Is needed. This can save money by using less chilled or heated water (not all AHUs use chilled or hot water circuits). Some external air is needed to keep the building's air healthy. To optimize energy efficiency while maintaining healthy indoor air quality (IAQ) , demand control (or controlled) ventilation (DCV) adjusts the amount of outside air based on measured levels of occupancy. Analog or digital temperature sensors may be placed in
1950-487: Is one of two or more operating modes for a building automation system; Unoccupied, Morning Warmup, and Night-time Setback are other common modes. Occupancy is usually based on time of day schedules. In Occupancy mode, the BAS aims to provides a comfortable climate and adequate lighting, often with zone-based control so that users on one side of a building have a different thermostat (or a different system, or sub system) than users on
2025-466: Is that ARCNET provides the sender with a concrete acknowledgment (or not) of successful delivery at the receiving end before the token passes on to the next node, permitting much faster fault recovery within the higher level protocols (rather than having to wait for a timeout on the expected replies). ARCnet also doesn't waste network time transmitting to a node not ready to receive the message, since an initial inquiry (done at hardware level) establishes that
2100-496: The HVAC controls industry. In 1996 Alerton announced a BACnet product line for HVAC controls, from the operator's workstation to small variable air volume (VAV) controllers. Automated Logic Corporation and Delta Controls soon followed suit. On July 12, 2017, BACnet reached a milestone with the issuance of the 1000th Vendor ID. Vendor IDs are assigned by ASHRAE and are distributed internationally. Those vendor identifiers can be viewed at
2175-527: The IEEE 1905.1 standard and verified by the nVoy auditing mark. These accommodate typically only IP-based networking but can make use of any existing wiring, and also integrate powerline networking over AC circuits, power over Ethernet low-power DC circuits, high-bandwidth wireless networks such as LTE and IEEE 802.11n and IEEE 802.11ac and often integrate these using the building-specific wireless mesh open standard Zigbee . Proprietary hardware dominates
2250-479: The RG-58 (50Ω) 'thin' Ethernet most widely used at that time was limited to a maximum run of 185 m (607 ft) from end to end. ARCNET had the disadvantage of requiring either an active or passive hub between nodes if there were more than two nodes in the network, while thin Ethernet allowed nodes to be spaced anywhere along the linear coax cable. However, ARCNET passive hubs were very inexpensive, being composed of
2325-490: The field bus Digital Addressable Lighting Interface (DALI). Lamps with DALI ballasts are fully dimmable. DALI can also detect lamp and ballast failures on DALI luminaires and signals failures. Shading and glazing are essential components in the building system, they affect occupants’ visual, acoustical, and thermal comfort and provide the occupant with a view outdoor. Automated shading and glazing systems are solutions for controlling solar heat gains and glare. It refers to
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2400-553: The pulses over a period of time. An example is a turbine flow meter transmitting flow data as a frequency of pulses to an input. Nonintrusive load monitoring is software relying on digital sensors and algorithms to discover appliance or other loads from electrical or magnetic characteristics of the circuit. It is however detecting the event by an analog means. These are extremely cost-effective in operation and useful not only for identification but to detect start-up transients , line or equipment faults, etc. Analog outputs control
2475-612: The type of computers that would be connected. This was in contrast to contemporary larger and more expensive computer systems such as DECnet or SNA , where a homogeneous group of similar or proprietary computers were connected as a cluster . The token-passing bus protocol of that I/O device-sharing network was subsequently applied to allowing processing nodes to communicate with each other for file-serving and computing scalability purposes. An application could be developed in DATABUS, Datapoint's proprietary COBOL -like language and deployed on
2550-596: The 135-2012 standard and it was republished as 135-2016. Carl stepped down as chair in June 2015. In June 2015, Bernhard Isler, from Siemens, became chair after serving 3 years as vice chair and 4 years as secretary. During Bernhard's term, 10 addenda were published for the 135-2016 standard. Once addenda to 135.1-2013 was also published. Bernhard stepped down as chair in June 2018. In June 2018, Michael Osborne from Reliable Controls, became chair after serving 3 years as secretary and 3 years as vice chair. The BACnet protocol defines
2625-546: The BACnet protocol began in June, 1987, in Nashville, Tennessee, at the inaugural meeting of the ASHRAE BACnet committee, known at that time as SPC 135P, "EMCS Message Protocol". The committee worked at reaching consensus using working groups to divide up the task of creating a standard. The working groups focused on specific areas and provided information and recommendations to the main committee. The first three working groups were
2700-410: The BACnet standard was republished twice, in 2001 and 2004, each time with new capabilities added to the standard. The 2001 version featured, among other things, extensions to support fire / life-safety systems. In June, 2004, 17 years after the first BACnet meeting and back in Nashville, William (Bill) Swan (a.k.a. "BACnet Bill") from Alerton began his four-year stint as committee chair. During his term
2775-574: The BACnet website Archived 2009-11-21 at the Wayback Machine . H. Michael (Mike) Newman, Manager of the Computer Section of the Utilities and Energy Management Department at Cornell University , served as the BACnet committee chairman until June, 2000, when he was succeeded by his vice-chair of 13 years, Steven (Steve) Bushby from NIST . During Steve Bushby's four-year term as committee chair
2850-446: The BTL working group ("BTL-WG"). The general activities of the BTL are: The BTL also provides testing services through BACnet Laboratories. The BTL Managers and BTL working groups of BACnet International administer the test Laboratories. All BTL-recognized BACnet Test Organizations are ISO 17025 accredited. In January, 2017, a new BTL certification program was announced. Under this program,
2925-648: The Data Type and Attribute Working Group, Primitive Data Format Working Group, and the Application Services Working Group. BACnet became ASHRAE/ANSI Standard 135 in 1995, and ISO 16484-5 in 2003. The Method of Test for Conformance to BACnet was published in 2003 as BSR/ASHRAE Standard 135.1. BACnet is under continuous maintenance by the ASHRAE Standing Standard Project Committee 135. BACnet had an almost immediate impact on
3000-466: The ability to trigger alarms when disconnected. Modern systems typically use power-over-Ethernet (which can operate a pan-tilt-zoom camera and other devices up to 30–90 watts) which is capable of charging such batteries and keeps wireless networks free for genuinely wireless applications, such as backup communication in outage. Fire alarm panels and their related smoke alarm systems are usually hard-wired to override building automation. For example: if
3075-401: The building) or other security systems such as closed-circuit television (CCTV) and motion detectors. Fire alarm systems and elevators are also sometimes linked to a BMS for monitoring. In case a fire is detected then only the fire alarm panel could close dampers in the ventilation system to stop smoke spreading, shut down air handlers, start smoke evacuation fans, and send all the elevators to
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3150-500: The control of daylight and solar energy to enter into built environment in relation to outdoor conditions, daylighting demands and solar positions. The common products include venetian blinds , roller shades , louvers , and shutters. They are mostly installed on the interior side of the glazing system because of the low maintenance cost, but also can be used on the exterior or a combination of both. Most air handlers mix return and outside air so less temperature/humidity conditioning
3225-755: The controller market. Each company has controllers for specific applications. Some are designed with limited controls and no interoperability, such as simple packaged roof top units for HVAC. Software will typically not integrate well with packages from other vendors. Cooperation is at the Zigbee/BACnet/LonTalk level only. Current systems provide interoperability at the application level, allowing users to mix-and-match devices from different manufacturers, and to provide integration with other compatible building control systems . These typically rely on SNMP , long used for this same purpose to integrate diverse computer networking devices into one coherent network. With
3300-501: The controller to send command and control signals to slave devices, and to other parts of the system. Inputs and outputs can be either digital or analog. Digital outputs are also sometimes called discrete depending on manufacturer. Controllers used for building automation can be grouped in three categories: programmable logic controllers (PLCs), system/network controllers, and terminal unit controllers. However an additional device can also exist in order to integrate third-party systems (e.g.
3375-404: The early days of Ethernet, an ARCNET passive hub could be easily manufactured in the field with 9 readily available parts (4 connectors, 4 resistors and a box to put them in). Passive hubs limited the distance between a node and an active hub to 30 m (100 ft). A passive hub could not be connected directly to another passive hub. Unused ports on both types of hubs had to be terminated with
3450-443: The embedded market. Even though ARCNET is now rarely used for new general networks, the diminishing installed base still requires support - and it retains a niche in industrial control. Original ARCNET used RG-62/U coaxial cable of 93 Ω impedance and either passive or active hubs in a star-wired bus topology. At the time of its greatest popularity, this was a significant advantage of ARCNET over Ethernet. A star-wired bus
3525-505: The first IBM PC was announced in 1981) over ten thousand ARCNET LAN installations were in commercial use around the world, and Datapoint had become a Fortune 500 company. As microcomputers took over the industry, well-proven and reliable ARCNET was also offered as an inexpensive LAN for these machines. ARCNET remained proprietary until the early-to-mid 1980s. This did not cause concern at the time, as most network architectures were proprietary. The move to non-proprietary, open systems began as
3600-473: The general availability of switched gigabit Ethernet and Quality of service capabilities in Ethernet switches has all but eliminated ARCNET today. At first the system was deployed using RG-62/U coaxial cable (commonly used in IBM mainframe environments to connect 3270 terminals and controllers), but later added support for twisted pair and fibre media. At ARCNET's lower speeds ( 2.5 Mbit/s ), Cat-3 cable
3675-454: The greater raw speed of Ethernet ( 10 Mbit/s , as compared with 2.5 Mbit/s for ARCnet) helped to increase Ethernet demand, and as more companies entered the market the price of Ethernet started to fall—and ARCNET (and Token Ring) volumes tapered off. In response to greater bandwidth needs, and the challenge of Ethernet, a new standard called ARCnet Plus was developed by Datapoint, and introduced in 1992. ARCnet Plus ran at 20 Mbit/s , and
3750-567: The ground floor and park them to prevent people from using them. Building management systems have also included disaster-response mechanisms (such as base isolation ) to save structures from earthquakes. In more recent times, companies and governments have been working to find similar solutions for flood zones and coastal areas at-risk to rising sea levels . Self-adjusting floating environment draws from existing technologies used to float concrete bridges and runways such as Washington's SR 520 and Japan's Mega-Float . Analog inputs are used to read
3825-591: The growing spectrum of capabilities and connections to the Internet of Things , building automation systems were repeatedly reported to be vulnerable, allowing hackers and cybercriminals to attack their components. Buildings can be exploited by hackers to measure or change their environment: sensors allow surveillance (e.g. monitoring movements of employees or habits of inhabitants) while actuators allow to perform actions in buildings (e.g. opening doors or windows for intruders). Several vendors and committees started to improve
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#17328515447833900-407: The last motion was sensed. A photocell placed outside a building can sense darkness, and the time of day, and modulate lights in outer offices and the parking lot. Lighting is also a good candidate for demand response , with many control systems providing the ability to dim (or turn off) lights to take advantage of DR incentives and savings. In newer buildings, the lighting control can be based on
3975-444: The local sensors, actuators and processing devices. Almost all multi-story green buildings are designed to accommodate a BAS for the energy, air and water conservation characteristics. Electrical device demand response is a typical function of a BAS, as is the more sophisticated ventilation and humidity monitoring required of "tight" insulated buildings. Most green buildings also use as many low-power DC devices as possible. Even
4050-461: The network interface card. Larger networks would have to be split into smaller networks, and bridged. The small number of possible nodes and the need to manually configure IDs was a disadvantage compared with Ethernet, particularly as large enterprise networks became common. To mediate access to the bus , ARCNET, like Token Ring, uses a token passing scheme, rather than the carrier sense multiple access approach of Ethernet. When peers are inactive,
4125-689: The number of committee working groups grew to 11, pursuing areas such as support for lighting, access control, energy utility/building integration, and wireless communications. In January 2006 the BACnet Manufacturers Association and the BACnet Interest Group of North America combined their operation in a new organization called BACnet International Archived 2020-08-17 at the Wayback Machine . In June 2008, in Salt Lake City, Dave Robin from Automated Logic Corporation took over
4200-504: The open protocol LonTalk specify how most such devices interoperate. Modern systems use SNMP to track events, building on decades of history with SNMP-based protocols in the computer networking world. Physical connectivity between devices was historically provided by dedicated optical fiber , ethernet , ARCNET , RS-232 , RS-485 or a low-bandwidth special purpose wireless network . Modern systems rely on standards-based multi-protocol heterogeneous networking such as that specified in
4275-536: The opposite side. A temperature sensor in the zone provides feedback to the controller, so it can deliver heating or cooling as needed. If enabled, morning warmup (MWU) mode occurs prior to occupancy. During Morning Warmup the BAS tries to bring the building to setpoint just in time for Occupancy. The BAS often factors in outdoor conditions and historical experience to optimize MWU. This is also referred to as optimized start . Some buildings rely on occupancy sensors to activate lighting or climate conditioning. Given
4350-412: The potential for long lead times before a space becomes sufficiently cool or warm, climate conditioning is not often initiated directly by an occupancy sensor. Lighting can be turned on, off, or dimmed with a building automation or lighting control system based on time of day, or on occupancy sensor, photosensors and timers. One typical example is to turn the lights in a space on for a half-hour since
4425-424: The recipient is able and ready to receive the larger message before it is sent across the bus. One further advantage that ARCNET enjoyed over collision-based Ethernet is that it guarantees equitable access to the bus by everyone on the network. Although it might take a short time to get the token depending on the number of nodes and the size of the messages currently being sent about, you will always receive it within
4500-517: The reins as the new committee chair after serving 4 years as vice chair. During Dave's term, 22 addenda were published for the 135-2008 standard and republished as 135-2010. Several addenda were published for 135-2010 and the standard was republished as 135-2012. In June 2012, in San Antonio, Carl Neilson from Delta Controls took over the reins as the new committee chair after serving 4 years as vice chair. During Carl's term, 12 addenda were published for
4575-419: The room very complex. It is common for room automation systems to employ a touchscreen as the primary way of controlling each operation. ARCNET Attached Resource Computer NETwork ( ARCNET or ARCnet ) is a communications protocol for local area networks . ARCNET was the first widely available networking system for microcomputers ; it became popular in the 1980s for office automation tasks. It
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#17328515447834650-413: The same time, due to the time required for the slower processors of the day to process and recover from collisions. ARCNET had slightly lower best-case performance (viewed by a single stream), but was much more predictable. ARCNET also has the advantage that it achieved its best aggregate performance under the highest loading, approaching asymptotically its maximum throughput. While the best case performance
4725-507: The security features in their products and standards, including KNX, Zigbee and BACnet (see recent standards or standard drafts). However, researchers report several open problems in building automation security. On November 11, 2019, a 132-page security research paper was released titled "I Own Your Building (Management System)" by Gjoko Krstic and Sipke Mellema that addressed more than 100 vulnerabilities affecting various BMS and access control solutions by various vendors. Room automation
4800-476: The smoke alarm is activated, all the outside air dampers close to prevent air coming into the building, and an exhaust system can isolate the blaze. Similarly, electrical fault detection systems can turn entire circuits off, regardless of the number of alarms this triggers or persons this distresses. Fossil fuel combustion devices also tend to have their own over-rides, such as natural gas feed lines that turn off when slow pressure drops are detected (indicating
4875-424: The space or room, the return and supply air ducts , and sometimes the external air. Actuators are placed on the hot and chilled water valves, the outside air and return air dampers. The supply fan (and return if applicable) is started and stopped based on either time of day, temperatures, building pressures or a combination. All modern building automation systems have alarm capabilities. It does little good to detect
4950-406: The speed or position of a device, such as a variable frequency drive , an I-P ( current to pneumatics ) transducer , or a valve or damper actuator . An example is a hot water valve opening up 25% to maintain a setpoint . Another example is a variable frequency drive ramping up a motor slowly to avoid a hard start. Digital outputs are used to open and close relays and switches as well as drive
5025-488: The use of technology to control external or internal shading devices (such as blinds, and shades) or glazing itself. The system has an active and rapid response to various changing outdoor data (such as solar, wind) and to changing interior environment (such as temperature, illuminance, and occupant demands). Building shading and glazing systems can contribute to thermal and lighting improvement from both energy conservation and comfort point of view. Dynamic shading devices allow
5100-956: The work of the BTL and WSPCert (the European BACnet certification body) is merged. This merger forms a single point of testing for both the BTL Mark and the Certificate of Conformance. Building automation Building automation ( BAS ), also known as building management system ( BMS ) or building energy management system ( BEMS ), is the automatic centralized control of a building's HVAC (heating, ventilation and air conditioning) , electrical, lighting , shading, access control , security systems , and other interrelated systems. Some objectives of building automation are improved occupant comfort, efficient operation of building systems, reduction in energy consumption, reduced operating and maintaining costs and increased security. BAS functionality may keep
5175-465: Was backward compatible with original ARCnet equipment. However, by the time ARCnet Plus products were ready for the market, Ethernet had captured the majority of the network market, and there was little incentive for users to move back to ARCnet. As a result, very few ARCnet Plus products were ever produced. Those that were built, mainly by Datapoint, were expensive, and hard to find. ARCNET was eventually standardized as ANSI ARCNET 878.1. It appears this
5250-467: Was later applied to embedded systems where certain features of the protocol are especially useful. ARCNET was developed by principal development engineer John Murphy at Datapoint Corporation in 1976 under Victor Poor , and announced in 1977. It was originally developed to connect groups of their Datapoint 2200 terminals to talk to a shared 8" floppy disk system. It was the first loosely coupled LAN-based clustering system, making no assumptions about
5325-664: Was less expensive than either, more reliable, more flexible, and by the late 1980s it had a market share about equal to that of Ethernet. Tandy/Radio Shack offered ARCNET as an application and file sharing medium for their TRS-80 Model II , Model 12 , Model 16 , Tandy 6000 , Tandy 2000 , Tandy 1000 and Tandy 1200 computer models. There were also hooks in the Model 4P 's ROM to boot from an ARCNET network. When Ethernet moved from co-axial cable to twisted pair and an "interconnected stars" cabling topology based on active hubs , it became much more attractive. Easier cabling, combined with
5400-433: Was less than Ethernet, the general case was equivalent and the worst case was dramatically better. An Ethernet network could collapse when too busy due to excessive collisions. An ARCNET would keep on going at normal (or even better) throughput. Throughput on a multi-node collision-based Ethernet was limited to between 40% and 60% of bandwidth usage (depending on source). Although 2.5 Mbit/s ARCNET could at one time outperform
5475-519: Was much easier to build and expand (and was more readily maintainable) than the clumsy linear bus Ethernet of the time. The "interconnected stars" cabling topology made it easy to add and remove nodes without taking down the whole network, and much easier to diagnose and isolate failures within a complex LAN. Another significant advantage ARCNET had over Ethernet was cable distance. ARCNET coax cable runs could extend 610 m (2,000 ft) between active hubs or between an active hub and an end node, while
5550-530: Was run from each port of the active hubs to a different location no more than 30 m (100 ft) away. A passive hub would then be attached to the end of the cable, and cables would be run locally from the passive hub, allowing connection of up to three nodes. In this way, a single 8-port active hub could be used to connect 24 networked devices over an area not exceeding 120 m (400 ft) in diameter. ARCNET allowed only 255 nodes per network. Node IDs for LAN workstations were typically set by DIP switches on
5625-420: Was when the name changed from ARCnet to ARCNET. Other companies entered the market, notably Standard Microsystems who produced systems based on a single VLSI chip, originally developed as custom LSI for Datapoint, but later made available by Standard Microsystems to other customers. Datapoint eventually found itself in financial trouble and eventually moved into video conferencing and (later) custom programming in
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