Multiuser SMS Based Wireless Electronic Notice Board
Abstract— This is the model for displaying notices in colleges on electronic notice board by sending messages in form of SMS through mobile; it is a wireless transmission system which has very less errors and maintenance. The hardware board contains microcontroller AT89c52 at the heart of the system. The microcontroller is interfaced with GSM Modem via MAX232 level convertor. It is used to convert RS232 voltage levels to TTL voltage levels and vice versa. The hardware also has a 64K EEPROM chip AT24C64. This EEPROM is used to store the timings and messages to be displayed. Hardware also contains a real time clock DS1307 to maintain track of time. A 16x2 Character LCD display is
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B. GSM Modem
A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem behaves like a dial-up modem. The main difference between them is that a dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves. Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate.
Generally, computers use AT commands to control modems. Reading of message from the SIM card inserted into the modem is done by sending the appropriate AT command to the modem.
In addition to the standard AT commands, GSM modems support an extended set of AT commands. These extended AT commands are defined in the GSM standards. Some common basic SMS related AT Commands are shown in table below:
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Fig.2. AT Commands
C. Display Unit
One of the most common devices attached to an 8051 is an LCD display. Here we have used 16x2- that means 2 rows and 16 characters. It is a Hitachi HD44780 compatible module, having 16 pins including 2 pins for backlight.
To program the LCD module, first we have to initialize the LCD by sending some control words. RS should be low and E should be high when we send control. R/W pin 0 mean write data or control to LCD and R/W pin 1 means read data from the LCD. To send a data to LCD, make RS high, R/W low, place
There are different types of telephone systems, the range can be from simple hand held domestic telephones to switch board telephone network systems used in business organisations. The features varies from the type of telephone systems its you are using and the different types of the hand set features they have. For example the “ Call Waiting” feature is for if you are talking on the phone and some one calls you and you can put the first caller on hold and talk to the second, and switch between the two callers. You can have "Call Forward", so that if you needed to forward the call to a different person with a different hand set you can forward this call in this way. Finally there is the "Call Answer" feature which means that if you are on the phone or not at home then the telephone system will answer your phone call and take a message and play it back for you.
Cellular and broadband phones normally include Long Distance, Voice Mail, Caller ID, Call Forwarding and more, usually at no additional charge. They also have Text Messaging and various forms of data service which are unavailable with a landline.
AT&T Inc. (AT&T), consolidated on October 5, 1983, is a holding company. The Company is a supplier of communications and computerized entertainment benefits in the United States and the world. The Company works through four sections: Business Solutions, Entertainment Group, Consumer Mobility and International. Its administrations offerings incorporate remote communications, information/broadband and Internet administrations, computerized video administrations, neighborhood and long-separate telephone administrations, telecommunications hardware, oversaw systems administration and discount administrations (www.digitaltrends.com). The Company offers administrations and items to buyers in the United States, Mexico and Latin America, and to organizations and different suppliers of telecommunications administrations around the globe. The Company likewise claims and works roughly three provincial games networks, and holds interests in another territorial games organize and a system devoted to diversion related programming, and additionally Internet intuitive amusement playing (www.digitaltrends.com).
Cellular and broadband phones normally include Long Distance, Voice Mail, Caller ID, Call Forwarding and more, usually at no additional charge. They also have Text Messaging and various forms of data service which are unavailable with a landline.
To begin with, a cell phone is short form for cellular phone. A cellular phone is also known as a cell phone, hand phone,phone,or mobile phone. You can make and receive telephone calls from anyway around the world with the help from radio links. These devices are connected to a lot of technology. A wise man ,Kenny Chesney, once said, “My mind is constantly going. For me to completely relax, I gotta get rid of my cell phone.”
The use of short-messaging systems (SMS) is becoming more mainstream due to the exponential increase in cell phone usage and other mobile devices. From messages sent through Twitter to emergency notifications broadcast through mobile networks, the short-messaging systems is becoming more ubiquitous.
3G technology was designed to support merge the existing cellular technologies such as GSM , TDMA,FDMA, CDMA and complete successfully result with new technologies as Wideband CDMA , CDMA 2000.Third generation is digital but not narrowband it is broadband. W-CDMA network is used for high capacity application signals and CDMA 2000 is the improved version of second generation CDMA IS-95.It focused on high speed internet access ,wide range market applications , new creativity , innovation and user benefits. By using 3G maximum 2Mbps speed is possible.
In Asia, Europe, Canada and the USA, telecommunication companies use W-CDMA technology with the support of around 100 terminal designs to operate 3G mobile networks.
Display - The space available on the computer desktop depends on the size of the monitor (computer screen) and on its
A mobile phone or mobile (also called cellphone and handphone) is an electronic device used for mobile telecommunications (mobile telephone, text messaging or data transmission) over a cellular network of specialized base stations known as cell sites. Most current cell phones connect to a cellular network consisting of switching points and base stations (cell sites) owned by a mobile network operator. In addition to the standard voice function, current mobile phones may support many additional services, and
GSM (Global System for Mobile communication) is a digital mobile telephony system which is TDMA based wireless network technology developed widely in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephony technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot.
As the GSM uses the combination of Time and FDM, the mobile is used to demultiplex the given channel and also it is responsible for accessing the channel more effectively and efficiently. The mobile device is used to transmit and receive the required data within in a given time frame and with if a give condition. With the help of mobile devices, there are many other services offered by the GSM to enable ad to support more efficient data transmission. These services can be SMS, MMS etc. All these services can only be accessed with the help of mobile devices which supports may other multimedia features like live calling, video calling etc. Every day,
DESIGN OF WIRELESS DATA MODEM PCB LAYOUT DESIGN USING CAD TOOL MICROCONTROLLER BASED SYSTEMS DESIGN DSP BASED SYSTEM DESIGN PSUEDO RANDOM SEQUENCE GENERATOR
A GSM network consists of several functional entities whose functions and interfaces are defined. The GSM network can be divided into following broad parts.
LED MATRIX (5x7): The display screen is made up of four 5 x 7 led matrix modules, resulting an 7 x 20 pixels display in 2-dimension. The size of each character is 5 x 7 in our design. With the display holding up to four characters one at a time, it allows a four digit hour and minute clock to be displayed simultaneously.