World Academy of Science, Engineering and Technology 46 2008
Design and Construction of MicrocontrollerBased Telephone Exchange System Aye Sandar Win
Almon Strowger was issued a patent on March 11, 1891 for the first automatic telephone exchange. The first exchange using the Strowger switch was opened in La Porte, Indiana in 1892 and initially subscribers had a button on their telephone to produce the required number of pulses by tapping. An associate of Strowgers' invented the rotary dial in 1896 which replaced the button. In 1943, Philadelphia was the last major area to give up dual service (rotary and button) . Telephone exchange is a system that allows and controls the sharing of phone lines between telephones and other communication devices. It is widely used by office, hotel applications and the business organizations. A telephone exchange system is useful for a bank or brokerage house speech system or the like, which can accommodate a large number of lines. It features internal calls without getting changed, because calls are routed internally. It has connectivity to the telephone network in most cases. It provides more features than the telephone network provides. The telephone exchange is also the private automated branch exchange. It is used on the subscriber’s private premises. It provides a switching facility for telephone on extension lines within the building and across the PSTN. Today, almost all PBXs use digital technology to control microprocessor components as public exchanges progressed from using analog technology to digital. PABXs are available in size ranging from a few extensions and one exchange line up to several thousands of extensions and hundred of exchange lines . A PABX is a telephone exchange that serves a particular business or office, as opposed to one a common carrier or Telephone Company operates for many businesses or for the general public . Even with the recent birth of the World Wide Web and other new generation digital communication techniques the public switched telephony network is still one of the most important communication systems in the world. The telephone exchange system is popular among organizations because of the communication freedom; it is capable of supplying its users with. Having a fast, efficient and user-friendly local phone network can often be a major requirement for a successful business organization. The popularity of the telephone exchange system can be seen by the extensive use of their applications around the globe. From this popularity the understanding of the fundamentals of an exchange system’s operation and its popularity are the primary motivator for this paper.
Abstract—This paper demonstrates design and construction of microcontroller-based telephone exchange system and the aims of this paper is to study telecommunication, connection with PIC16F877A and DTMF MT8870D. In microcontroller system, PIC 16F877 microcontroller is used to control the call processing. Dial tone, busy tone and ring tone are provided during call progress. Instead of using ready made tone generator IC, oscillator based tone generator is used. The results of this telephone exchange system are perfect for homes and small businesses needing the extensions. It requires the phone operation control system, the analog interface circuit and the switching circuit. This exchange design will contain eight channels. It is the best low cost, good quality telephone exchange for today’s telecommunication needs. It offers the features available in much more expensive PBX units without using high-priced phones. It is for long distance telephone services.
Keywords—Control software, DTMF receiver and decoder, hook sensing, microcontroller system, power supply, ring generator and oscillator based tone generator. I. INTRODUCTION NY business cannot survive without the availability of telephone. Communication is very important in today’s business world. If the business is small, then...
References: http://www.innovexpo.itee.uq.edu.au/2001/projects/s369342/poster.pdf http://www.nps.gov/nhl/DOE_dedesignations/Telephone.htm http://en.wikipedia.org/wiki/Private_branch_exchange#PBX_functions http://www.mitedu.freeserve.co.uk/Design/dcpsu.htm http://www.radio-electronics.com/info/circuits/lc_lowpassfilter/ lc_lpf.php http://en.wikipedia.org/wiki/ powersupply http://en.wikibooks.org/wiki/Communication_Systems/Telephone_Syste m R.Blake. “The Telephone System. Comprehensive Electronic Communication”, 1997, pp. 325-344. S.J.Bigelow, J.J. Carr, S.Winder, “Understanding Telephone Electronics,” Fourth Edition, Butterworth-Heinemann, 2001.
        
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