Broadcast technologies

Perhaps the oldest or most basic forms of public communication are staples such as over-the-air television, sirens, and radio. More modern components (using the same concept) might include lights and Giant Voice systems. These all have one thing in common: they broadcast indiscriminately to anyone who has the means to receive the message; whether they are simply in the immediate area or require some sort of receiving device.

Broadcast technologies use point-to-point communications methodology and may either require infrastructure or not. Examples of broadcast technologies requiring infrastructure might include such things as Reverse 911 and broadcast-affiliate networks.

Infrastructure-independentedit

Broadcast technologies that do not depend on man-made infrastructure to convey communication may be least susceptible to disruption during disasters and emergencies. Some examples of infrastructure-independent technologies are:

• Short-wave Radio

Short-wave (or Amateur) radio is a relatively long range method of communicating using radio waves. Because of the nature of radio wave propagation, communications made via short-wave radio can be intercepted and heard by anyone with the proper equipment and knowledge. However, due to their reliance only on electrical power (which can be obtained via batteries, solar, and other alternative means) and Earth's ionosphere, they are ideal for some of the worst case emergency scenarios. One disadvantage may be that one requires training and licensing to transmit using a short-wave radio, in many countries.

• Two-way Radio

Two-way radio consists of at least two devices (typically portable and hand-held) that are capable of transmitting and receiving communications to each other, using radio waves. Similar to short-wave, this type of communication is also able to be intercepted and heard by anyone with the proper equipment. However, unlike short-wave, this communication equipment is restricted by range (usually several miles, at most), but is relatively simple to operate and the main power source is usually provided by batteries. Two-way radios are in-use by many emergency responders on a daily basis, so they require minimal concentration to operate in the stress of an emergency situation, since the person operating it is already familiar with it. Additionally, many non-professionals may use unlicensed two-way radios, as is common with CB radio, Family Radio Service or PMR446.

• Weather Radio

A weather radio is a device which receives normal and emergency weather broadcasts. It may automatically turn on whenever an emergency is eminent or occurring, providing an alarm as well as a description of the situation. Anyone with a weather radio device can receive these broadcasts.

• Internet Based Communication

There is increasingly an opportunity to use infrastructure-independent network connection, sometimes called Network-centric emergency notification, for emergency communication. The emergence of initiatives such as Google's Project Loon offer opportunities for networked communication when infrastructure-dependent communication is hindered in emergency situations.

Each device has its own pros and cons given the emergency situation.

Infrastructure-dependentedit

Broadcast technologies that depend on man-made infrastructure to convey communication are susceptible to disruption if any part of that infrastructure is overloaded, damaged or otherwise destroyed. Some examples of infrastructure-dependent technologies are:

• Audio Public Address Systems

A system which can provide audio (usually spoken language) messaging capability, usually consisting of microphone devices, wiring, and speakers installed in public areas of buildings. These systems are typically located indoors or in smaller outdoor areas with multiple speakers, due to their speakers' individual volume being too limited for large areas. Usually connected together by wiring requiring electricity, these systems may be vulnerable to electrical disruption or any other event which results in the wires being severed or disconnected.

• WMT Public Address Systems

Wireless Mobile Telephony (WMT) PA Systems refers to PA paging and intercom systems that use any form of Wireless Mobile Telephony System such as GSM networks instead of a centralized amplifier to distribute the audio signal to paging locations across a building or campus, or other location. The GSM mobile Networks are used to provide the communication function. At the transmission end, a PSTN Telephone, mobile phone, VOIP phone or any other communication device that can access and make audio calls to a GSM based mobile SIM card can communicate with it. At the receiving end, a GSM transceiver receives these network transmissions and reproduce the analogue audio signal via a Power Amplifier and speaker. The work on this was pioneered by Stephen Robert Pearson of Lancashire, England who successfully applied for and was granted patents for the systems which incorporate control functionality in addition to the audio announcement capabilities. The use of the WMT (GSM) networks means that live announcements can be made from anywhere to anywhere in the world where there is WMT connectivity. The patents cover all forms of WMT i.e. 2G, 3G, 4G ..... xxG. A UK company called Remvox Ltd (REMote VOice eXperience) has been appointed under license to develop and manufacture products based upon this technology.

• L.E.D. Electronic Signs

LED electronic signs use light-emitting diodes to display messages when connected over a network to an emergency communication system. LED signs, when deployed in large numbers on a network, can be used as visual alternatives to traditional audio public address systems. LED Signs are able to communicate effectively in loud environments where audio PA systems can be ineffective. When deciding whether or not to include LED electronic signs as part of an emergency communication system, it is important to realize that a lack of hearing-impaired persons does not negate the need for visual signs. Explosions and other events can render many hearing-able people effectively deaf, necessitating the inclusion of a visual alternative to audio PA systems. LED electronic signs have multiple valuable attributes that enhance public communications:

• Some emergency communication systems can deliver, share, and prioritize the display of messages on LED signs that have been sent by multiple people and systems.
• LED signs, when connected to an emergency communication system, have the ability to project the communication in a specific direction while loud speakers generally radiate communication in many directions.
• LED signs are manufactured in a large variety of shapes and sizes, with some models designed specifically for indoor use and very bright models designed for outdoor use.
• Because LEDs consume very little electricity, power over Ethernet (PoE) and power over RS232 can be used in conjunction with UPS power located in wiring closets to keep these devices functioning for a significant period of time during a general power outage in a building.
• Like audio PA systems, visual PA systems composed of LED signs are network-attached appliances that, unlike computer screen popup messages (more information about this technology, below), text messages, phone calls, etc., represent `Always On` technologies, which can be relied on to deliver the communication in real time without the risk that the device might be off, in use, or out of power.
• LED signs are available that can display messages in a single color, red-green-yellow characters, or full color, which allows for color coding of emergency messages when desired. These types of signs can be relatively affordable compared to digital signs and are easy to install, making them a common choice for organizations wishing to use electronic forms of visual communication. Common means of connecting these devices include Ethernet or serial communication cabling.
• In combination with audio PA systems, these devices can be used to achieve compliance with the ADA requirements for equal access to communications.

Government, public and private entities may use LED electronic signs for any purpose ranging from advertising to emergency management. For emergency use of these types of signs, it is often necessary to electronically control them in a unified and coordinated manner, using one of or a mixture of specialized hardware and software. There exist at least a few commercial methods that advertise this capability, for example Siemens Sygnal, Inova Solutions, and MessageNet Connections.

• Combination Audio/Visual Public Address Devices

Any device which combines the audio capability of a PA system with the visual capability of an electronic sign (usually of the L.E.D. variety). These, too, rely on infrastructure to operate.

• Digital Signage

Throughout the first decade of the twenty-first century, plasma televisions and other flat-panel LCD televisions and monitors have become commonplace in businesses, hospitals, schools, post-secondary institutions, government, airports, shopping malls, and financial institutions, etc.; with that prominence, they have begun to play a major role in emergency communications. Similar to combination audio/visual PA devices, yet much more advanced, digital signage monitors are capable of displaying high-resolution videos, pictures, multimedia presentations, text and other high-definition media. Typically digital signage can provide video, audio, presentation graphics and web page content abilities that can support the communication of an emergency. In addition, the graphical multimedia capabilities of digital signage can enable emergency wayfinding or egress routing that can be customized to the event and location of the emergency and the affected people.

Digital signage is often more expensive than relatively simple LED electronic signs, which makes it more sensible to garner as much utility from it as possible for maximum return on investment. Over time, though, this technology has become more affordable, resulting in digital signage being used in more venues, usually for non-emergency purposes such as displaying news, weather, directions, etc. Other emerging uses of digital signage related to emergency communication systems include: displaying building floorplans, maps, evacuation routes, and first responder situational awareness (such as showing a firefighter where a fire has been detected).

Emergency communication systems and digital signage are integrated in many verticals including outdoor, in retail spaces, in hospitals and clinics. More recently, smart city companies are using prominent screens around the urban landscape to convey critical messages to the city's population. These emergency systems have technical integrations where the emergency message will interrupt and override any advertisements currently playing or scheduled.citation needed

• Giant Voice Systems

A system focused on providing auditory messaging capability for large outdoor areas, being able to project voice and sounds over large distances, without the need for a large number of speakers. These systems are commonly used on military bases and chemical manufacturing plants, for example. These technologies allow specific instructions to be broadcast over a large area, however they may be subject to substantial echo and weather-related effects; and furthermore, environmental noise may interfere with their effectiveness. This forces unnatural speech, on the part of the warning originator, and may render the communication difficult for the listener to comprehend. This fact has prompted some to primarily rely on tones and coded signals that the audience must be familiar with in advance. Even though these can be heard over a large area, the high-powered speakers require a connection to the communication originator via some sort of infrastructure, meaning they might have a certain level of vulnerability to disruption in the collection infrastructure. The alternative to the use of Giant Voice systems is to deploy large arrays of smaller lower power speakers, this approach also allows for greater specificity of message by location. When properly synchronized these speaker arrays can deliver more comprehensible speech, however these arrays will involve larger amounts of supporting infrastructure. Siemens and Federal Signal are two of the major commercial providers of Giant Voice systems being actively deployed at military bases, government facilities and industry, currently; with Federal Signal being one of the first providers of these types of systems, after the Pearl Harbor attack.