DOCSLIB.ORG

Cordless Phones and Cellular Modems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Cordless Phones and Cellular Modems SNS COLLEGE OF TECHNOLOGY, (An Autonomous Institution) COIMBATORE- 641 035 ELECTRONICS FOR HOME APPLIANCES LIMITED RANGE CORDLESS PHONES AND CELLULAR MODEMS By, GANGATHARAN S 17MC013 10/10/2019 III-B.E.MCT 1 CORDLESS PHONES 10/10/2019 SNS COLLEGE OF TECHNOLOGY 2 CONTENT • Introduction. • Cordless telephones. • History of cordless telephones. • Types of cordless phones. • Analog phones. • Digital phones. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 3 INTRODUCTION means CORD WIRE CORDLESS means WIRELESS Cordless system is basically general term of cordless telephones and cordless telecommunication. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 4 CORDLESS TECHNOLOGY Cordless originates from the technique that made it possible for subscribes to connect a small base station to their telephones, thereby attaining a limited degree of mobility. It is full of duplex communication system that use radio to connect a portable handset and a dedicated base station, which is then connected to a dedicated telephone line with a specific telephone number on a Public Switched Telephone Network. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 5 CORDLESS TELEPHONE Cordless telephone is a telephone with a wireless handset that communication via radio waves with a base station connected to a fixed telephone line, usually within a limited range of its base station. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 6 HISTORY OF CORDLESS TELEPHONE A jazz musician named Terl Pall invented George Sweigert, an radio operator and a version of the cordless phones in 1965 inventor from is largely recognized as the but could not market her invention as its father of the cordless phones. He two mile range caused radio signals to submitted a patent application in 1966 for interfere with aircraft. a “full duplex wireless communications apparatus”. In the 1980s, a no of manufacturers, Sweigert, a radio operator in world war II including Sony, introduced cordless stationed at the south pacific island phones for the consumer market. developed the full duplex- concept for untrained personnel, to improve Since the 1980s, several companies have battlefield communications for senlor entered the cordless- phone market: commanders. Vtech, Uniden, Philips, Glgaset, Panasonic, Etc,. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 7 TYPES OF CORDLESS PHONES CORDLESS TELEPHONES ANALOG DIGITAL CT0 CT1 DECT PHS 10/10/2019 SNS COLLEGE OF TECHNOLOGY 8 ANALOG PHONES • These are least expensive. • Better voice quality than digital phones. • Use 5.8 GHz frequency band. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 9 DRAWBACKS OF ANALOG PHONES • Are of shorter rand than digital phones • This is not a secure transmission. • We can listen voices by using RF scanner or any comparable device. • Conference calls are not allowed. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 10 DIGITAL PHONES • In 1994, digital cordless phones in the 900 MHz frequency range were introduced. • Digital signals allowed the phones to be more secure and decreased eavesdropping. • This technology enabled the digital voice transmission to be spread over multiple frequencies, improving privacy and reducing interference between different subscribers. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 11 CELLULAR MODEMS 10/10/2019 SNS COLLEGE OF TECHNOLOGY 12 CELLULAR MODEMS • It is a short form for modulator / demodulator. • It is the device that adds wireless 3G or 4G (LTE) connectivity to a laptop or desktop computer. • Cellular modems communicate with the internet through cell phone towers. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 13 WHAT IS THE PURPOSE OF MODEM? • Basically, a modem is used for transmitting and receiving data over a communication channel, such as twisted pair telephone lines, coaxial cables, and optical fibres. Currently the purpose of a modem is to convert a computer’s data stream to analog format so that it can be transmitted over the analog telephone line. • At the source, modulation techniques are used to convert digital data (0’s and 1’s) into analog form for transmission across the channel. At the destination, the received analog signal is converted to digital data via demodulation. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 14 TYPES OF MODEMS • External modem: This is a modem separated from the system unit in the computer case. it is connected to the serial port of the computer by means of a cable. it is connected to the telephone wall jack by another cable. • Internal modem: An internal modem is a circuit board (a modem card) that can be added to the system unit of the computer. it takes one of the expansion slots. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 15 ADVANTAGES • The main benefit of a modem is that it allows you and your devices to access the internet and communicate with the outside world. • The downside is that a modem can allow viruses and hackers to enter your network. • It is easy to maintain. • It is easy to upgrade the equipment's. • It is used in areas where cables can not be laid out due to its wireless nature. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 16 DISADVANTAGES • It offers less data rate compare to wired networks such as fibre optics, DSL, etc. • The data rate varies based on wireless standards such as GSM, CDMA, LTE, etc. • Macro cells are affected by multipath signal loss. • As the communication is over the air, it has security vulnerabilities. • It requires higher cost in order to setup cellular network infrastructure. 10/10/2019 SNS COLLEGE OF TECHNOLOGY 17 .
Load more

Recommended publications
  • Re-Construction and Definition of New Branches & Hierarchy of Sciences
    Philosophy Study, July 2016, Vol. 6, No. 7, 377-416 doi: 10.17265/2159-5313/2016.07.001 D DAVID PUBLISHING New Perspective for the Philosophy of Science: Re-Construction and Definition of New Branches & Hierarchy of Sciences Refet Ramiz Near East University In this work, author evaluated past theories and perspectives behind the definitions of science and/or branches of science. Also some of the philosophers of science and their specific philosophical interests were expressed. Author considered some type of interactions between some disciplines to determine, to solve the philosophical/scientific problems and to define the possible solutions. The purposes of this article are: (i) to define new synthesis method, (ii) to define new perspective for the philosophy of science, (iii) to define relation between new philosophy perspective and philosophy of science, (iv) to define and organize name, number, relations, and correct structure between special science branches and philosophy of science, (v) to define necessary and sufficient number of branches for philosophy of science, (vi) to define and express the importance and place of new philosophy of science perspective in the new system, (vii) to extend the definition/limits of philosophy of science, (viii) to re-define meanings of some philosophical/scientific theories, (ix) to define systematic solution for the conflicts, problems, confusions about philosophy of science, sciences and branches of science, (x) to define new branches of science, (xi) to re-construct branches and hierarchy of science, (xii) to define new theories about science and branches of science. Author considered R-Synthesis as a method for the evaluation of the philosophy, philosophy of science, sciences and branches of science.
    [Show full text]
  • Cellular and Mobile Communications Course and Subject File
    Cellular and Mobile Communications Course and Subject File Contents: 1. Cover Page 2. Syllabus copy 3. Vision of the Department 4. Mission of the Department 5. PEOs and POs 6. Course objectives and outcomes 7. Brief notes on the importance of the course and how it fits into the curriculum 8. prerequisites 9. Instructional Learning Outcomes 10. Course mapping with PEOs and POs 11. Class Time Table 12. Individual Time Table 13. Micro Plan with dates and closure report 14. Detailed notes 15. Additional topics 16. University Question papers of previous years 17. Question Bank 18. Assignment topics 19. Unit wise Quiz Questions 20. Tutorial problems 21. Known gaps ,if any 22. Discussion topics 23. References, Journals, websites and E-links 24. Quality Control Sheets 25. Student List 26. Group-Wise students list for discussion topics GEETHANJALI COLLEGE OF ENGINEERING AND TECHNOLOGY DEPARTMENT OF Electronics and Communication Engineering (Name of the Subject) : CELLULAR AND MOBILE COMMUNICATIONS Programme : UG Branch: ECE Version No : 02 Year: IV Updated on :03/12/2015 Semester: II No.of pages :250 Classification status (Unrestricted / Restricted ) Distribution List : Prepared by : 1) Name : B.SUNEETHA 2) Sign : 3) Design : Assistant Professor 4) Date : 03/12/2015 Verified by : 1) Name : * For Q.C Only. 2) Sign : 1) Name : 3) Design : 2) Sign : 4) Date : 3) Design : 4) Date : Approved by : (HOD ) 1) Name : 2) Sign : 3) Date : Vision of the department To impart quality technical education in Electronics and Communication Engineering emphasizing analysis, design/synthesis and evaluation of hardware/embedded software using various Electronic Design Automation (EDA) tools with accent on creativity, innovation and research thereby producing competent engineers who can meet global challenges with societal commitment.
    [Show full text]
  • Tese 2014 01 27
    Tesis sobre la afectación de la tecnología a la concepción del espacio en la vivienda por el habitante. A través del análisis de diferentes elementos, se trata de generar un modelo de irrupción para determinar pautas evolutivas de tendencias futuras, atendiendo a diferentes modificaciones y circunstancias dentro del ámbito de estudio. Tesis doctoral de ANGEL RICO PAINCEIRAS Director: Eduard Bru Bistuer Universitat Politécnica de Catalunya Escola Técnica Superior d’Arquitectura de Barcelona Departamento de Proyectos Arquitectónicos Barcelona 2013 ADICADO A RAINHA indice INTRODUCCIÓN 01C A P I T U L O 04C A P I T U L O CONCLUSIONES 255 07 OBJETO DEL ESTUDIO VARIABLES DISRUPTIVAS 271 11 ÁMBITO TENDENCIAS DE FUTURO 279 DESMATERIALIZACIÓN 285 CONVERGENCIA TECNOLÓGICA 291 DISOLUCIÓN 293 ARQUITECTO Y ARQUITECTURA 295 C A P I T U L O VECTORES 02C A P I T U L O 05 REFERENCIAS 31 TIEMPO BIBLIOGRÁFICA 306 39 TECNOLOGÍA ARTÍCULOS 310 43 VELOCIDAD ETIMOLÓGICAS 312 51 ADAPTACIÓN PERSONALES 318 ANÁLISIS 03C A P I T U L O ANÁLISIS FUNCIONAL 83 MODELO 89 ILUMINACIÓN 115 ASCENSOR 127 TELÉFONO 135 RADIO 149 NEVERA 155 TELEVISIÓN 181 TELEFONÍA MÓVIL 189 C.P_LA RED ANÁLISIS ESPACIAL 203 DISTRIBUCIÓN 217 REALIDAD AUMENTADA 229 REALIDAD VIRTUAL 235 OCUPANTES Y USUARIOS 1 INTRODUCCIÓN 1.1. OBJETIVO DEL ESTUDIO 1.2 ÁMBITO • GEOGRÁFICO • SOCIAL • TEMPORAL 1.3 PUNTO DE PARTIDA • ACOTACIÓN DEL ESTUDIO • INTRODUCCIÓN HISTÓRICA 1 INTRODUCCIÓN 1.1. OBJETIVO DEL ESTUDIO Con el presente estudio pretendo hacer una reflexión sobre la evolución del concepto de espacio en la vivienda influido por el cambio tecnológico. Para dicho estudio será preciso tener en cuenta otros elementos que en los últimos años han sufrido importantes cambios, como los factores sociológicos, tanto en las estructuras de las familias como en el estilo de vida.
    [Show full text]
  • Mobile Communication
    MOBILE COMMUNICATION UNIT 1. Wireless Communication 1.1 Basics 1.2 Advantages of wireless communication 1.3 Electromagnetic waves. 1.4 Frequency Spectrum used. 1.5 Paging system. 1.6 Cordless Telephone System. 1.7 Cellular Telephone System 1.8 Comparison of above wireless communication systems. 1.9 Propagation considerations a) Range b) Atmospheric Effect c) Geographic Effect d) Signal Fading e) Doppler Effect What is Wireless Communication? Communication Systems can be Wired or Wireless and the medium used for communication can be Guided or Unguided. In Wired Communication, the medium is a physical path like Co-axial Cables, Twisted Pair Cables and Optical Fiber Links etc. which guides the signal to propagate from one point to other. Such type of medium is called Guided Medium. On the other hand, Wireless Communication doesn’t require any physical medium but propagates the signal through space. Since, space only allows for signal transmission without any guidance, the medium used in Wireless Communication is called Unguided Medium. If there is no physical medium, then how does wireless communication transmit signals? Even though there are no cables used in wireless communication, the transmission and reception of signals is accomplished with Antennas. Antennas are electrical devices that transform the electrical signals to radio signals in the form of Electromagnetic (EM) Waves and vice versa. These Electromagnetic Waves propagates through space. Hence, both transmitter and receiver consist of an antenna. What is Electromagnetic Wave? Electromagnetic Waves carry the electromagnetic energy of electromagnetic field through space. Electromagnetic Waves include Gamma Rays (γ – Rays), X – Rays, Ultraviolet Rays, Visible Light, Infrared Rays, Microwave Rays and Radio Waves.
    [Show full text]
  • IL SERVIZIO DI RADIOAMATORE L’Attività Di Radioamatore, Che Ha Preso L’Avvio Agli Inizi Del XX Secolo, È Una Delle Più Antiche Nel Campo Delle Telecomunicazioni
    Un po’ di storia… IL SERVIZIO DI RADIOAMATORE L’attività di radioamatore, che ha preso l’avvio agli inizi del XX secolo, è una delle più antiche nel campo delle telecomunicazioni. La definizione formale, ed ufficiale, del servizio di radioamatore, è contenuta nel regolamento Internazionale delle Telecomunicazioni, stilato e pubblicato a cura della International Telecommunication Union (I.T.U.). Il radiantismo costituisce l’unico mezzo attraverso il quale singoli individui, distanti fra loro anche migliaia di chilometri, possono venire a contatto e a conoscenza senza coinvolgere alcun intermediario. Questa é l’impostazione generale dell’attività radiantistica secondo le convenzioni della I.T.U. e della I.A.R.U. (International Amateur Radio Union), l’ente costituito dall’unione di tutte le Associazioni di radioamatori del mondo, e che le rappresenta ad alto livello internazionale. QUANDO É NATO IL RADIANTISMO Gli inizi del radiantismo prendono il loro avvio, in analogia con quelli della Radio in generale, dai fenomeni fisici ed elettrici preliminarmente studiati dai precursori del settore. Infatti, dopo le antiche e poco più che casuali ricerche di Ampere, Faraday, Galvani e altri, nonché dopo i primi inquadramenti teorici da parte di Maxwell ed Hertz, fu Guglielmo Marconi che (mettendo in pratica applicazione tutto quanto da altri anticipato, assieme alle proprie intuizioni) sviluppò il primo sistema di telecomunicazione ad onde hertziane, atto a trasmettere e ricevere messaggi via radio. Era il 1895: i mezzi a disposizione, i sistemi
    [Show full text]
  • History of Mobile Phones
    History of mobile phones From Wikipedia, the free encyclopedia Jump to: navigation, search The history of mobile phones charts the development of devices which connect wirelessly to the public switched telephone network. Early devices were bulky and consumed high power and the network supported only a few simultaneous conversations. Modern cellular networks and microprocessor control systems allow automatic and pervasive use of mobile phones for voice and data communications. The transmission of speech by radio has a long and varied history going back to Reginald Fessenden's invention and shore-to-ship demonstration of radio telephony, through the Second World War with military use of radio telephony links. Mobile telephones for automobiles became available from some telephone companies in the 1950s. Hand-held radio transceivers have been available since the Second World War. Mobile phone history is often divided into generations (first, second, third and so on) to mark significant step changes in capabilities as the technology improved. Contents [hide] 1 Pioneers of radio telephony o 1.1 Cellular concepts o 1.2 Before cellular networks . 1.2.1 Origins . 1.2.2 Radio Common Carrier . 1.2.3 Rural Radiotelephone Service 2 Emergence of commercial mobile phone services 3 Handheld cell phone 4 First generation: Cellular networks 5 Second generation: Digital networks 6 Third generation: High speed IP data networks and mobile broadband 7 Fourth generation: All-IP networks 8 Satellite mobile 9 Patents 10 See also 11 Notes 12 References 13 External links [edit] Pioneers of radio telephony By 1930, telephone customers in the United States could place a call to a passenger on a liner in the Atlantic Ocean.
    [Show full text]
  • Sweigert V Goodman Doc 300 714 2021
    Case 1:18-cv-08653-VEC-SDA Document 300 Filed 07/14/21 Page 1 of 34 U.S. DISTRICT COURT FOR THE SOUTHERN DISTRICT OF NEW YORK SWEIGERT CIVIL CASE #: V. 1:18-CV-08653-VEC GOODMAN JUDGE VALERIE E. CAPRONI AMENDED AND CORRECTED AFFIDAVIT OF D. GEORGE SWEIGERT IN SUPPORT OF OPPOSITION TO DEFENDANT GOODMAN’S MOTION FOR SUMMARY JUDGMENT (ECF 279/280) EXHIBITS IN SEPARATE DOCUMENT REPLACES DOCUMENT 295 1. The undersigned makes this statement as D. George Sweigert under the penalties of perjury. At the onset, the undersigned apologizes for the length of this document, but as the Defendant has made dozens of allegations, based on this subject matter, it cannot be avoided. 2. As a preliminary matter, the undersigned takes offense to the term “holster sniffer” to describe the Plaintiff’s non-profit volunteer support of local agencies by the Defendant and the ghost writer attorney that assisted with the pleading papers presently under review (ECF 279/280). The Court should understand that this is the equivalent of using the N word in the undersigned’s opinion. Part of this affidavit summarizes the lack of decorum by the Defendant that has ever been present in this litigation. 3. The undersigned is primarily interested in retaining his reputation in the fields of critical infrastructure protection and emergency management, which took a lifetime to build, from the Defendant. This document describes the undersigned’s motivation, to address what the 1 Case 1:18-cv-08653-VEC-SDA Document 300 Filed 07/14/21 Page 2 of 34 undersigned avers are false statements made about the Plaintiff that have harmed the Plaintiff and his technical, ethical and professional reputation.
    [Show full text]
  • Unit-I Cellular Mobile Radio Systems
    UNIT-I CELLULAR MOBILE RADIO SYSTEMS Limitations of conventional mobile systems over cellular mobile system Limitations of conventional mobile telephone systems: One of many reasons for developing a cellular mobile telephone system and deploying it in many cities is the operational limitations of conventional mobile telephone systems: limited service capability, poor service performance, and inefficient frequency spectrum utilization. 1. Limited service capability: A conventional mobile telephone system is usually designed by selecting one or more channels from a specific frequency allocation for use in autonomous geographic zones, as shown in Fig.1.1. The communications coverage area of each zone is normally planned to be as large as possible, which means that the transmitted power should be as high as the federal specification allows. The user who starts a call in one zone has to reinitiate the call when moving into a new zone because the call will be dropped. This is an undesirable radio telephone system since there is no guarantee that a call can be completed without a handoff capability. The handoff is a process of automatically changing frequencies as the mobile unit moves into a different frequency zone so that the conversation can be continued in a new frequency zone without redialing. Another disadvantage of the conventional system is that the number of active users is limited to the number of channels assigned to a particular frequency zone. Fig1.1 Conventional Mobile System 2. Poor Service Performance: In the past, a total of 33 channels were all allocated to three mobile telephone systems: Mobile Telephone Service (MTS), Improved Mobile Telephone Service (IMTS) MJ systems, and Improved Mobile Telephone Service (IMTS) MK systems.
    [Show full text]
  • Kr^ Radi Tmlin Ical
    . - ' , I ■ G l a iU S : I C o a <i c h : ~ K i l o» i w a t t -Sw itospfi3ruces lip th e ^ A/aboma’s*s 1BearBrifant ' . red and wlwhite for • ! 5 ^ (s college fofootball’s .. A preview; ooj / f h e n e i u 2 2 S ! state energif, h ls b u s y s<season—-CI , qfl-tffnc winitnr^ — Dl • Jft j m m i. _ ^ _ I 76th year, N<^ o . 3 3 3 . , . Twin Falls, Idcdaho Sund)day; November 229.1981 I " 5 0 ^ ■ Ss - K r^tmlin1 to sseek I radiical arms< s cutts ^ m m " - GENEVA, Switzerland;nd (UPI) — dism antleI theirtl 630 ^ 2 0 , SS-5 and thtl e arm s lalks would bc a "historic ■ I J L Soviet arms negotiatorllor Yuli A, sS-4 missilssiies already deployed dd ate,” Kvitsinksy said Saturdayly the1] Kremlin throughoutIt E astern Europe, Kvjtsinskv! 45. said Mo.loscow has .................. ------- wHl see>c-a-“ rad}cai“- oor r even com^ However,T, lhe soviets insist British adopteda “an honest and coiconstcucllve plete reduction of nucica:iear arms In and Frcnch:h nuclear missiles, as well approach”a towards the ncgollatibnsnc Europe at talks wllh Uie• UnitedUr States as Am erican:an nuclear-armed bombers anda would aim for “ radicalII reductionsi starting Monday. and submariarines stationed in Europe, inir medium-range nuclcarar arm s in W' s In Hamburg, West GenJermany, U.S. be included^ in any head-count of Ihe Europe.E a rm s negotiator Paul Nit:'Iltze em erged forces tolKfi)C reduced.
    [Show full text]
  • S DX@WW $425WW400A 425 DX News #400 [1/3] 2 January 1999 No 400
    S DX@WW $425WW400A 425 DX News #400 [1/3] 2 January 1999 No 400 BID: $425WW400A =========================== *** 4 2 5 D X N E W S *** **** DX INFORMATION **** =========================== Edited by I1JQJ & IK1ADH /---------------------------------------------------------------------------\ ! Information, reports and suggestions must be sent to: ! ! ! ! Mauro Pregliasco, I1JQJ: DX information ! ! (e-mail [email protected] - BBS [email protected]) ! ! Massimo Balsamo, IK1GPG: QSL Managers/QSL Routes ! ! (e-mail [email protected] - BBS [email protected]) ! ! Maurizio Bertolino, I1-21171: 425 DX News WWW Pages ! ! (e-mail [email protected]) ! \---------------------------------------------------------------------------/ ************************************ * TO ALL OUR READERS * * WARMEST THOUGHTS AND BEST WISHES * * FOR A WONDERFUL HOLIDAY * * AND A VERY HAPPY NEW YEAR * ************************************ 5A - Veronica, IK3ZAW and Martino, IK3RIY [425DXN 399] are now active as 5A1IC until 4 January. QSL via IK3ZAW (Veronica Della Dora, Piazza Fiume 14, 30126 Lido di Venezia - VE, Italy) CE - Laurence, GM4DMA will active (CW and SSB) from southern Patagonia between 5 and 24 January. QSL via home call (preferably through the bureau). [TNX DX News Sheet] D3 - Gabriel, D3SAF lives in northern Angola and is currently active on 10-20 meters. He expects to operate on 40 metres as well, while there is little hope for 80 and 160. QSL via I3LLH. [TNX The Daily DX] FO_mar - Suggested frequencies for the 7-13 January operation by Pekka, OH1RY and Jaakko, OH1MA from the Marquesas (OC-027) [425DXN 399] are: 1824.5, 3507, 3799, 7007, 7077, 10107, 18077, 18145, 24897, 24945 and the usual DX frequencies on the other bands. Look for FO0KOL (OH1RY) on SSB and FO0SIL (OH1MA) on CW.
    [Show full text]
  • History of Mobile Phones
    History of mobile phones From Wikipedia, the free encyclopedia Jump to: navigation, search [hide] • 1 Pioneers of radio telephony • 2 Emergence of commercial mobile phone services • 3 First generation: Cellular networks • 4 Second generation: Digital networks • 5 Third generation: High speed IP data networks • 6 Growth of mobile broadband and the emergence of 4G • 7 Patents • 8 See also • 9 Notes • 10 References • 11 External links [edit] Pioneers of radio telephony of Murray, Kentucky. He applied this patent to "cave radio" telephones and not directly to cellular telephony as the term is currently understood.[1] In 1910 Lars Magnus Ericsson installed a telephone in his car, although this was not a radio telephone. While travelling across the country, he would stop at a place where telephone lines were accessible and using a pair of long electric wires he could connect to the national telephone network.[2] In Europe, radio telephony was first used on the first-class passenger trains between Berlin and Hamburg in 1926. At the same time, radio telephony was introduced on passenger airplanes for air traffic security. Later radio telephony was introduced on a large scale in German tanks during the Second World War. After the war German police in the British zone of occupation first used disused tank telephony equipment to run the first radio patrol cars.[citation needed] In all of these cases the service was confined to specialists that were trained to use the equipment. In the early 1950s ships on the Rhine were among the first to use radio telephony with an untrained end customer as a user.
    [Show full text]