Theindustry standard way of representing display sizes is publishing their length in inches. The screen-to-body ratio is a measure which relates to the size of the screen bezels. The bigger the ratio, the smaller the bezels are, meaning the display takes up a larger area on the device's front.
Some phones feature a camera that gives them the ability to work as a digital camera. Often (though not always) the camera is also able to shoot video. The most important characteristics of a camera are the resolution (measured in megapixels), lens focus type (either fixed or automatic) and the presence of a flash. The flash could be either LED (single or even double) or xenon. The number of megapixels is not always a good measurement of the quality of the photos, but if you plan to print pictures, you would generally get higher quality ones out of higher megapixel cameras. Auto focus lens are not a guarantee of better image quality, but fixed focus cameras are usually inferior. Most importantly, only auto focus cameras can allow shooting of really close objects - i.e. macro shooting. Some phones offer optical zoom but those are rare. Most use digital zoom, which degrades the quality of the photo. Cameras that can work in "video mode" are characterized by the maximum resolution and framerate (frames per second or fps) of the recorded video.
The loudspeaker is a small sound driver fitted within a mobile phone, or other communication device, which is used to produce sound. Traditionally, loudspeakers on mobile phones are used to produce sound alerts for events such as incoming calls, incoming messages and alarms. Since mobile phones have started doubling as portable music players in recent years, users have begun using their built-in speakers for playback of music. Acknowledging this new type of use of the mobile phone loudspeaker, manufacturers have begin to equip their music or video-centric mobiles with more powerful loudspeakers or even a pair of loudspeakers for accurate stereo reproduction and enhanced spatial effects. Loudspeakers are also used to reproduce voice calls out loud, thus allowing users to deal with calls hands-free or even have conference calls with others in the same room (that use of the mobile phone is called a speakerphone, which is not to be confused with a loudspeaker). Loudspeaker implementation can vary from model to model. For example, in order to save space and make phones thinner, some manufacturers don't use a dedicated loudspeaker but instead use the earpiece speaker to produce sound alerts as well. One way or another, whether you use it for fun, conference calls or just for plain ringing, there is one single thing that's important - loudness. We had explored this in depth in our reviews besides the casual subjective remark, but in 2007 we decided it was time we took a more scientific approach. So we got ourselves a handy piece of equipment - a digital noise/loudness meter - in order to start measuring objectively that all-important aspect of modern handsets - how loud is the loudspeaker in reality. So, for the record, here is how our test setup goes. We do our tests in one and the same quiet room taking sound measurements with the handset loudspeaker facing the microphone at a distance of exactly 1 m. We do three different tests. For each test we make several consecutive measurements - we usually disregard the highest and the lowest readings and we take the average value of the rest. The three tests are as follows: 1) A phone ringing. We use an old-school ringtone, resembling the ringing of an old phone. It seems that most phones do well when we use it. 2) Pink noise. We use a sample of pink noise. Our readings with it are pretty indicative on how well the handset loudspeaker would fare with standard music. Teenagers definitely appreciate a handset that will allow them to crank up the volume as high as possible. 3) Human voice, male. This is an important test, since if you tend the use the loudspeaker for speakerphone purposes, loudness is really important, regardless of whether you are in a conference room or in your car.
In addition to pure voice calls, all GSM carriers also offer messaging services and messaging has been a core service since the beginning of GSM mobile telephony. Mobile messaging ranges from SMS, through EMS, to IM and Email.