Microphone and speakers in mobile phones allow communication between two people. Initially, the first devices transmitted the signal picked up by the microphone without any processing, which also led to the transmission of ambient noise, while the third millennium devices using a single microphone have begun to process the signal through filters in order to reduce or remove the background noise.
Newer models are now characterized by two microphones, one of which is placed near the mouth, while the other is generally placed in the opposite part or in any case is very distant, this distance allows the user to have two different signals between the two microphones, so that the main microphone is able to adjust optimally the voice of the user.
While the second microphone, also called environmental microphone, records the noise of the surrounding environment (noise). By performing the difference of the two signals, isolation of the voice is achieved. The dual microphone can in some cases also be used for video recording with stereo sound.
Mobile phone speakers may present more functionality: Single classical solution, which in the early models did not allow the use of hands-free feature, whereas models have appeared since 1995 that allowed the use of this function.
Dual solution used since 2000 for many phones, these have a box specifically designed for normal communication and used for hands-free and possibly also for listening and viewing media files.
They have also increased the ports, Alcatel Phone Cases and connection methods to other systems such as infrared (IR) data transmission, Bluetooth and wi-fi connection via USB cable. The ability to connect headphones, headsets, microphones and hands-free devices. Some models can also accommodate additional memory cards (Secure Digital (SD)) to increase memory or even managing two SIM cards and Alcatel Phone Cases with two different phone numbers on the same phone.
Finally, there are also satellite phones which allows phone calls from virtually anywhere in the world. They are phones that ensure operation even in extreme environments that is extremely hot, cold or humid. Use strong but lightweight materials, employ batteries with increased autonomy and are equipped with several useful gadgets for the most varied purposes and contingencies.
Mobile phones contain a SIM card that identifies the user. Each device is identified, regardless of its brand by the International Mobile Station Equipment Identity or IMEI that is obtained by typing on the keyboard, the sequence * #06#. It should be recorded, IMEI helps network operators lock the device in the event of theft. This identifier should not be confused with the IMSI contained in the SIM card.