How Does Touch Screen of Mobile Work?

Every kind of touch-screens whether it’s of mobile phone or tablets or even touch-screen of desktop screens runs on same principle described below in a very simpler manner.

In older times the touch screen used a thin layer of flexible polyester film attached over a coat of glass or plastic. Other coatings such as criss-crossed or indistinguishable wires are also used in place of it.

Now when top layer is pressed over the lower layer with the help of a finger or its stylus, these invisible wires get intersect with each other thus will interrupt the flow current resulting change in direction which helps the device in deciding where is the touch located on screen. Here, a minimum amount of touch needs to apply to observe the result. In such older kind of touch screen technology, the sensitivity gets decreasing towards the edges due to out-dated technology but nowadays capacitive touch-screens are available which uses its smart technology so that the sensitivity of the touch screen remains constant & uniform through the screen.

In this technology, a capacitive film is place over the main screen, holds current which is purposely flown for this technology. Now when this film is touched by finger or stylus, this reduces the amount of current flowing at the contact point of screen.

Now as we know that there is nothing like invisible wires pressed hence, due to the capacitive screen can locate the contact point sensitively such that it is uniform throughout the screen with a slightest touch. Signals travel from the touch screen to the processor as electrical impulses. The processor uses software to analyze the data and determine the features of each touch. This includes size, shape and location of the affected area on the screen. If necessary, the processor arranges touches with similar features into groups. If you move your finger, the processor calculates the difference between the starting point and ending point of your touch. The processor uses its gesture-interpretation software to determine which gesture you made. It combines your physical movement with information about which application you were using and what the application was doing when you touched the screen.

The processor relays your instructions to the program in use. If necessary, it also sends commands to the iPhone's screen and other hardware. If the raw data doesn't match any applicable gestures or commands, the iPhone disregards it as an extraneous touch.

All these steps happen in an instant -- you see changes in the screen based on your input almost instantly. This process allows you to access and use all of the iPhone's applications with your fingers.

                                                                                                                Written By

A.Devasena

Associate Professor/ ECE Dept.

How Call has been created between any cell Phones?

How call has been created between the cell phones?

Each AMPS-capable cellular telephone includes a numeric assignment module(NAM) in read-only memory. The NAM contains the telephone number of the phone, which is assigned by the service provider, and the serial number of the phone, which is assigned by the manufacturer. When the phone is turned on, it transmits its serial number and phone number to the Mobile Telephone Switching Office ( MTSO) the MTSO maintains a database with information about mobile units that have been reported stolen and uses serial number to lock out stolen units. The  MTSO  uses the phone number for billing purposes. If the phone is used in a remote city, the service is still billed to the user's local service provider. 

When a call is placed, the following sequence of events occurs:

1. The subscriber initiates a call by keying in the telephone number of the called party and presses the send key.

2. The MTSO verifies that the telephone number is valid and that the user is authorized

to place the call; some service providers require the user to enter a PIN (personal identification number) as well as the called number to counter theft.

3. The MTSO issues a message to the user's cell phone indicating which traffic channels to use for sending and receiving.

4. The MTSO sends out a ringing signal to the called party. All of these operations(steps 2 through 4) occur within 10 s of initiating the call.

5. When the called party answers, the MTSO establishes a circuit between the two parties and initiates billing information.

6. When one party hangs up, the MTSO releases the circuit, frees the radio channels, and completes the billing information.

Written by A.Devasena.

Associate Professor/ECE

THE HARE AND THE TORTOISE

                                                                                            
                                                     

A Hare was making fun of the Tortoise one day for being so slow.

Do you ever get anywhere? he asked with a mocking laugh.

Yes, replied the Tortoise, "and I get there sooner than you think. I'll run you a race and prove it."

The Hare was much amused at the idea of running a race with the Tortoise, but for the fun of the thing he agreed. So the Fox, who had consented to act as judge, marked the distance and started the runners off.

The Hare was soon far out of sight, and to make the Tortoise feel very deeply how ridiculous it was for him to try a race with a Hare, he lay down beside the course to take a nap until the Tortoise should catch up.

The Tortoise meanwhile kept going slowly but steadily, and, after a time, passed the place where the Hare was sleeping. But the Hare slept on very peacefully,and when at last he did wake up, the Tortoise was near the goal. The Hare now ran his swiftest, but he could not overtake the Tortoise in time.

The race is not always to the swift.

   

N.Premkumar

Associate Professor/Mech