1. MEGAPHONE
A megaphone, speaking-trumpet, bullhorn, blowhorn, or loud hailer is a portable, usually hand-held, cone-shaped horn used to amplify a person’s voice towards a targeted direction. This is accomplished by channeling the sound through the megaphone, which also serves to match the acoustic impedance of the voice cords to the air. The natural human voice tends to spread evenly in all directions, whereas when it is sent through a megaphone, the sound is concentrated in a given direction and the coupling of its energy to the air optimised.[1] The trade-off is that if a listener is to the side, it is more difficult to hear what is being said.
2.TELEPON KABEL
Telepon merupakan alat komunikasi yang digunakan untuk menyampaikan pesan suara (terutama pesan yang berbentuk percakapan). Kebanyakan telepon beroperasi dengan menggunakan transmisi sinyal listrik dalam jaringan telepon sehingga memungkinkan pengguna telepon untuk berkomunikasi dengan pengguna lainnya.
Prinsip dasar telepon
Ketika gagang telepon diangkat, posisi telepon disebut off hook. Lalu sirkuit terbagi menjadi dua jalur di mana bagian positifnya akan berfungsi sebagai Tip yang menunjukkan angka nol sedangkan pada bagian negatif akan berfungsi sebagai Ring yang menunjukkan angka -48V DC. Kedua jalur ini yang nantinya akan memproses pesan dari sender untuk sampai ke receiver. Agar dapat menghasilkan suara pada telepon, sinyal elektrik ditransmisikan melalui kabel telepon yang kemudian diubah menjadi sinyal yang dapat didengar oleh telepon receiver. Untuk teknologi analog, transmisi sinyal analog yang dikirimkan dari central office (CO) akan diubah menjadi transmisi digital. Angka-angka sebagai nomer telepon merupakan penggabungan antara nada-nada dan frekuensi tertentu yang kemudian dinamakan Dual-tone multi-frequency DTMF dan memiliki satuan Hertz. Hubungan utama yang ada dalam sirkuit akan menjadi on hook ketika dibuka, lalu akan muncul getaran. Bunyi yang muncul di telepon penerima menandakan telepon telah siap digunakan.
3.GELOMBANG ELEKTROMAGNETIC
Electromagnetic wave is a phenomenon taking the form of self-propagating waves in a vacuum or in matter. EMR has both electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation.
Electromagnetic radiation is classified according to the frequency of its wave. In order of increasing frequency and decreasing wavelength), these are radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. The eyes of various organisms sense a small and somewhat variable window of frequencies called the visible spectrum. The photon is the quantum of the electromagnetic interaction and the basic "unit" of light and all other forms of electromagnetic radiation and is also the force carrier for the electromagnetic force.
EM radiation carries energy and momentum that may be imparted to matter with which it interacts.
Theory
James Clerk Maxwell first formally-postulated Electromagnetic waves. These were subsequently confirmed by Heinrich Hertz. Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave.
According to Maxwell's equations, a spatially-varying electric field generates a time-varying magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form a propagating electromagnetic wave. A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.
4.FIBER OPTIC
An optical fiber is a thin, flexible, transparent fiber that acts as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication. Fibers are used instead of metal wires because signals travel along them with less loss and are also immune to electromagnetic interference. Fibers are also used for illumination, and are wrapped in bundles so they can be used to carry images, thus allowing viewing in tight spaces. Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers.
Optical fiber typically consists of a transparent core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those which can only support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a larger core diameter, and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,050 meters (3,440 ft).
Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with heat. Special optical fiber connectors are used to make removable connections.
5.Wireless
wireless communication is the transfer of information without the use of wires.[1] The distances involved may be short (a few meters as in television remote control) or long (thousands or millions of kilometers for radio communications). The term is often shortened to "wireless". It encompasses various types of fixed, mobile, and portable two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of wireless technology include GPS units, garage door openers and or garage doors, wireless computer mice, keyboards and headsets, satellite television and cordless telephones.
Introduction
Wireless operations permits services, such as long range communications, that are impossible or impractical to implement with the use of wires. The term is commonly used in the telecommunications industry to refer to telecommunications systems (e.g. radio transmitters and receivers, remote controls, computer networks, network terminals, etc.) which use some form of energy (e.g. radio frequency (RF), infrared light, laser light, visible light, acoustic energy, etc.) to transfer information without the use of wires.[2] Information is transferred in this manner over both short and long distances.
