A mobile phone is a recent invention in the field of communication technology. You can use this device not only for receiving calls, but also for dialing, mailing and also to communicate with other compatible devices. The conversations made through this device are not protected. There is a possibility for interception. These mobiles can use either analogue system or digital system. Your handset gets the identity through your mobile phone number and the network which is provided by the service provider.
Every mobile phone has been equipped with an antenna which is embedded within the device itself. This device has been operated with the huge support of radio signals. While you chat through your instrument, it brings your voice after converting it as a radio signal to the nearby tower station. Then that tower will send your voice with the help of your network to your friend or neighbor or your colleague.
While you receive a call from others, the signals first reach the closest base station. Your signals are detected with an element called receiver and converted as radio waves in the base station itself. After that the waves will be reconverted as voice and it reaches your instrument. Not only for receiving the signals but also for making calls, network coverage is an essential one.
Suppose you get network outside your promises but you could not get the network within the promise, the lack of transmission power must be the only drawback. If the signals are very weak, it will not be able to penetrate into buildings. Therefore the service providers have to set towers within certain kilometers to avoid disturbances.