A communications system is a collection of individual communications networks, transmission systems, relay stations, tributary stations, and data terminal equipment (DTE) usually capable of interconnection and interoperation to form an integrated whole. The components of a communications system serve a common purpose, are technically compatible, use common procedures, respond to controls, and operate in union. Telecommunications is a method of communication (e.g., for sports broadcasting, mass media, journalism, etc.). A communications subsystem is a unit or operational assembly that is smaller than the larger assembly under consideration.

An optical communication system is any form of telecommunication that uses light as the transmission medium. Equipment consists of a transmitter, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal. Fiber-optic communication systems transmit information from one place to another by sending light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information.

A radio communication system is composed of several communications subsystems that give exterior communications capabilities. A radio communication system comprises a transmitting conductor in which electrical oscillations or currents are produced and which is arranged to cause such currents or oscillations to be propagated through the free space medium from one point to another remote therefrom and a receiving conductor at such distant point adapted to be excited by the oscillations or currents propagated from the transmitter.

Power line communication systems operate by impressing a modulated carrier signal on power wires. Different types of power line communications use different frequency bands, depending on the signal transmission characteristics of the power wiring used. Since the power wiring system was originally intended for transmission of AC power, the power wire circuits have only a limited ability to carry higher frequencies. The propagation problem is a limiting factor for each type of power line communications.

A duplex communication system is a system composed of two connected parties or devices which can communicate with one another in both directions. The term duplex is used when describing communication between two parties or devices. Duplex systems are employed in nearly all communications networks, either to allow for a communication “two-way street” between two connected parties or to provide a “reverse path” for the monitoring and remote adjustment of equipment in the field.

Examples of communications subsystems include the Defense Communications System (DCS).

A tactical communications system is a communications system that

(a) Is7 used within, or in direct support of, tactical forces,

(b) Is designed to meet the requirements of changing tactical situations and varying environmental conditions,

(c) provides securable communications, such as voice, data, and video, among mobile users to facilitate command and control within, and in support of, tactical forces, and

(d) Usually requires extremely short installation times, usually on the order of hours, in order to meet the requirements of frequent relocation.

An Emergency communication system is any system (typically computer based) that is organized for the primary purpose of supporting the two way communication of emergency messages between both individuals and groups of individuals. These systems are commonly designed to integrate the cross-communication of messages between are variety of communication technologies.

Navigation system

A navigation system is a (usually electronic) system that aids in navigation. Navigation systems may be entirely on board a vehicle or vessel, or they may be located elsewhere and communicate via radio or other signals with a vehicle or vessel, or they may use a combination of these methods.

Navigation systems may be capable of:

· containing maps, which may be displayed in human readable format via text or in a graphical format

· determining a vehicle or vessel’s location via sensors, maps, or information from external sources

· providing suggested directions to a human in charge of a vehicle or vessel via text or speech

· providing directions directly to an autonomous vehicle such as a robotic probe or guided missile

· Providing information on nearby vehicles or vessels, or other hazards or obstacles.

· Providing information on traffic conditions and suggesting alternative directions.

Types of navigation systems:

· Automotive navigation system.

· Marine navigation system.

· Global Positioning System, a group of satellites and computers that can provide information on any person, vessel, or vehicle’s location via a GPS receiver.

· GPS navigation device, a device that can receive GPS signals for the purpose of determining the device’s location and possibly to suggest or give directions.

· Surgical navigation system, a system which determines the position of surgical instruments in relation to patient images such as CT or MRI scans.

· Inertial guidance system, a system which continuously determines the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external reference.

· Robotic mapping, the methods and equipment by which an autonomous robot is be able to construct (or use) a map or floor plan and to localize itself within it.

· Web navigation

Aircraft Flight Control systems:

A conventional fixed-wing aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft’s direction in flight. Aircraft engine controls are also considered as flight controls as they change speed.

The fundamentals of aircraft controls are explained in flight dynamics. This article centers on the operating mechanisms of the flight controls.

Primary controls:

Generally, the primary cockpit flight controls are arranged as follows.

· a control yoke (also known as a control column), center stick or side-stick (the latter two also colloquially known as a control or joystick), governs the aircraft’s roll and pitch by moving the ailerons (or activating wing warping on some very early aircraft designs) when turned or deflected left and right, and moves the elevators when moved backwards or forwards

· Rudder pedals, or the earlier, pre-1919 “rudder bar”, to control yaw, which move the rudder; left foot forward will move the rudder left for instance.

· Throttle controls to control engine speed or thrust for powered aircraft.

The control yokes also vary greatly amongst aircraft. There are yokes where roll is controlled by rotating the yoke clockwise/counter clockwise (like steering a car) and pitch is controlled by tilting the control column towards you or away from you, but in others the pitch is controlled by sliding the yoke into and out of the instrument panel (like most Cessna’s, such as the 152 and 172), and in some the roll is controlled by sliding the whole yoke to the left and right (like the Cessna 162). Centre sticks also vary between aircraft. Some are directly connected to the control surfaces using cables, others (fly-by-wire airplanes) have a computer in between which then controls the electrical actuators.

Even when an aircraft uses variant flight control surfaces such as a V-tail ruddervator, flaperons, or elevons, to avoid pilot confusion the aircraft’s flight control system will still be designed so that the stick or yoke controls pitch and roll conventionally, as will the rudder pedals for yaw. The basic pattern for modern flight controls was pioneered by French aviation figure Robert Esnault-Pelterie, with fellow French aviator Louis Blériot popularizing Esnault-Pelterie’s control format initially on Louis’ Blériot VIII monoplane in April 1908, and standardizing the format on the July 1909 Channel-crossing Blériot XI. Flight control has long been taught in such fashion for many decades, as popularized in ab initioinstructional books such as the 1944 work Stick and Rudder.

In some aircraft, the control surfaces are not manipulated with a linkage. In ultra light aircraft and motorized hang gliders, for example, there is no mechanism at all. Instead, the pilot just grabs the lifting surface by hand (using a rigid frame that hangs from its underside) and moves it.

Secondary controls:

In addition to the primary flight controls for roll, pitch, and yaw, there are often secondary controls available to give the pilot finer control over flight or to ease the workload. The most commonly available control is a wheel or other device to control elevator trim, so that the pilot does not have to maintain constant backward or forward pressure to hold a specific pitch attitude (other types of trim, for rudder and ailerons, are common on larger aircraft but may also appear on smaller ones). Many aircraft have wing flaps, controlled by a switch or a mechanical lever or in some cases are fully automatic by computer control, which alter the shape of the wing for improved control at the slower speeds used for takeoff and landing. Other secondary flight control systems may be available, including slats, spoilers, air brakes and variable-sweep wings.

Radar Electronic Warfare:

Electronic warfare (EW) refers to any action involving the use of the electromagnetic spectrum or directed energy to control the spectrum, attack an enemy, or impede enemy assaults via the spectrum. The purpose of electronic warfare is to deny the opponent the advantage of, and ensure friendly unimpeded access to, the EM spectrum. EW can be applied from air, sea, land, and space by manned and unmanned systems, and can target humans, communications, radar, or other assets.

The electromagnetic environment:

Military operations are executed in an information environment increasingly complicated by the electromagnetic (EM) spectrum. The electromagnetic spectrum portion of the information environment is referred to as the electromagnetic environment (EME). The recognized need for military forces to have unimpeded access to and use of the electromagnetic environment creates vulnerabilities and opportunities for electronic warfare (EW) in support of military operations.

Within the information operations construct, EW is an element of information warfare; more specifically, it is an element of offensive and defensive counter information.

Electronic warfare applications:

Electronic warfare is any military action involving the use of the EM spectrum to include directed energy (DE) to control the EM spectrum or to attack an enemy. This is not limited to radio or radar frequencies but includes IR, visible, ultraviolet, and other less used portions of the EM spectrum. This includes self-protection, standoff, and escort jamming, and anti-radiation attacks. EW is a specialized tool that enhances many air and space functions at multiple levels of conflict.

The purpose of EW is to deny the opponent an advantage in the EM spectrum and ensure friendly unimpeded access to the EM spectrum portion of the information environment. EW can be applied from air, sea, land, and space by manned and unmanned systems. EW is employed to support military operations involving various levels of detection, denial, deception, disruption, degradation, protection, and destruction.

EW contributes to the success of information operations (IO) by using offensive and defensive tactics and techniques in a variety of combinations to shape, disrupt, and exploit adversarial use of the EM spectrum while protecting friendly freedom of action in that spectrum. Expanding reliance on the EM spectrum increases both the potential and the challenges of EW in information operations. The entire core, supporting, and related information operations capabilities either directly use EW or indirectly benefit from EW.

The principal EW activities have been developed over time to exploit the opportunities and vulnerabilities that are inherent in the physics of EM energy. Activities used in EW include: electro-optical, infrared and radio frequency countermeasures; EM compatibility and deception; EM hardening, interference, intrusion, and jamming; electronic masking, probing, reconnaissance, and intelligence; electronics security; EW reprogramming; emission control; spectrum management; and wartime reserve modes.


Certification is a critical element in the safety-conscious culture on which civil aviation is based. The legal purpose of avionics certification is to document a regulatory judgment that a device meets all applicable regulatory requirements and can be manufactured properly. At another level, beneath the legal and administrative machinery of regulatory approval, certification can be regarded differently. It can be thought of as an attempt to predict the future. New equipment proposed for certification has no service history. Certification tries, in effect, to provide credible predictions of future service experience for new devices — their influences on flight crews, their safety consequences, their failure rates, and their maintenance needs. Certification is not a perfect predictor, but historically it has been quite a good one.


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