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Welcome to the new home of the Celtnet Mobiles in formation site. This page is the eighth in a series of eight articles that takes you through how mobile phones work. You can either page through the aritcles, below, or you can use the navigation menu on the left to find the page you want.
In this article I'm actually going to take apart my old and trusted Sony Ericsson T200: one of the first of the truly pocket-sized GSM mobile phones. It was a wonderful little phone in it's time and though superceded many times over by now it remains a good model for how GSM mobile phones look when taken apart. After all, it contains all the modules and components of a modern phone apart from memory expansion sites.
The phone itself is very compact, literally palm-sized with a greyscale screen and all the usual buttons on the front. The back shows the covering of the battery bay which is easily slid out of the way. Also at the back is the aerial (brass) which can be connected to an external extension to improve reception. The phone also had side buttons for activation and voice recording. Just about the only feature not on the T200 which is essentially ubiquitous on any modern phone is a camera. In some respects, for this article at lest, it's a good thing that the T200 does not have a camera as this would complicate the circuitry of the phone and we require a relatively simple view for this article at least. |
Turning the phone over reveals the covering for the batter bay. This slides easily away and reveals the battery itself (see image to the left). This battery is a Lithium-Ion unit and represents the first generation of phones to hold these power units. They allowed the phones to be much smaller as the batteries were smaller and more powerful than earlier generations. These phones also had several days' standby time and up to 10h talk time. |
The battery can be easily removed and this reveals the battery bay itself. Beneath the battery, withing its own housing and secured by a metal clip lies the mobile phone's SIM card (indicated on the image to the far left). Within the battery bay there is also some information as to the nature and serial numbers of the phone. The image on the right gives a closer view of the SIM card and how it fits into the phone's housing. |
Sliding back the clip that holds the SIM card in place allows the SIM to pop out of its housing so that it can be esily removed from the phone. You can now see how the SIM card sits on six pins within its housing which make electrical contact with the FLASH RAM on the SIM card. These contacts are gold to maximize electrical contact. The same is essentially true of the battery which interfaces with five pins at the top of the battery bay; allowing both charging of the battery and the powering of the phone from the battery. |
Inside the Mobile Phone
The phone itself is secured by four TORX-6 screws which are easily removed with the correct screwdriver. Removing these allows the front of the phone to be detached from the back, revealing the front of the mobile phone's mainboard (also known as a motherboard). This reveals the white covering of the keyboard contacts, the mobile phone's screen which is shielded with copper around the edges to isolate it from radio interference and the internal housing of the phone's aerial. You can also see the fixings for the microphone at the phone's base and the speaker at the top. Effectively, all the phone's communication devices are held at the front of the phone's motherboard. Which should mean that electronic components are all isolated at the back of the mobile phone's motherboard. |
Removing the motherboard is simply a case of flipping the phone over and the motherboard simply falls out into your hand. The image on the left shows the motherboard's back and the rear housing of the phone itself. As you can see from this image, the back of the motherboard contains all the electronic devices for the phone with the connectors at the back. The front of the motherboard (above) houses all the communications devices for the phone, with their connections at the back. This means that the mainborad of the mobile phone is actually a pair of motherboards sandwiched together. The next section details what the various electronic components on the back of the motherboard actually do. |
Going from top to bottom, you can see the brass, external, portion of the aerial at the top. Next you have the back of the screen, shileded by a steel backing. Below the screen and to the right is the display control which again is shielded with a steel cover. Nestled between the display and the display control unit is the battery connector unit. After these components come the main electronic components. Below the screen and to the left isi the RF unit, the chip that actually composes the RF signal for transmission and which decodes the incoming RF signal to the phone. Below this is the main CPU which handles all the functions of the phone. This is effectively the phone's 'brain' and it controls the other chips on the motherboard as well as accepting and interpreting all the informaiton from the SIM card and the input devices. The next section details what the various electronic components on the back of the motherboard actually do. Indeed, the SIM card connector is to the immediate right of the CPU, allowing direct communication between the two devices. Below the CPU is the Analogue to Digital Converter (A/D Converter) and it is this that converts the analogue voice signal of the user into a digital signal and which converts the incoming digital signal into an analogue voice signal that can be played through the mobile phone's speakers. Finally we have the black connector at the base of the motherboard which provides both for power connections and for data connections to the phone. |
Conclusion
The images and the information above has given you an overview of the insides of a modern mobile phone and the main components of the phone. You will also have seen how few components the phone actually has. This is because all the main components are part of the main chips on the motherboard, which allows the phone to work with little power and gives long standby and talk times for your mobile phone.
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