On "complexity per cubic inch" scale, cell phones are of the most intricate devices that people use on daily basis. Modern cell phones can process millions of calculations per second on owing to compress, decompress the voice stream. They can transmit and receive on hundreds of FM channels, switching channels in sync with base stations as phone moves between cells.
Cell phone apart to find few individual parts:
Ø A microscopic microphone
Ø A speaker
Ø A LCD or plasma display
Ø A keyboard
Ø An antenna
Ø A Battery
Ø An amazing circuit board containing the spirit of the phone
This circuit board is the heart of the system. The below shown circuit board – Ericsson Model
In the above picture several components are identified. In the left, Analog-to-Digital and Digital-to-Analog conversion chips are seen. A-to-D and D-to-A conversion is very important in digital audio. The DSP is a "Digital Signal Processor", a highly customized processor designed to perform signal manipulation calculations at high speed. The DSP is rated at about 40 MIPS (Millions of Instructions per Second) and handles all the signal compression and decompression. The microprocessor (Ericsson phones use the ASIC version of the Z-80) and memory handle all of the housekeeping chores for the keyboard and display, deal with authority and control signaling with a base station and also manage the rest of the functions on the board. The RF and power section handles power management and recharging and also pacts with the hundreds of FM channels. At last, the RF (Radio Frequency) amplifiers handle signals in and out of the antenna.
Amazing Fact behind is that the functionality --- which 30 years ago would have filled the entire floor of an office building --- now the same fits into a single package that sets comfortably in the palm of our hand