Dynamic Loudspeaker Principle

A current-carrying wire in a magnetic field experiences a magnetic force perpendicular to the wire.

An audio signal source such as a microphone or recording produces an electrical "image" of the sound. That is, it produces an electrical signal that has the same frequency and harmonic content, and a size that reflects the relative intensity of the sound as it changes. The job of the amplifier is to take that electrical image and make it larger -- large enough in power to drive the coils of a loudspeaker. Having a "high fidelity" amplifier means that you make it larger without changing any of its properties. Any changes would be perceived as distortions of the sound since the human ear is amazingly sensitive to such changes. Once the amplifier has made the electrical image large enough, it applies it to the voice coils of the loudspeaker, making them vibrate with a pattern that follows the variations of the original signal. The voice coil is attached to and drives the cone of the loudspeaker, which in turn drives the air. This action on the air produces sound that more-or-less reproduces the sound pressure variations of the original signal.
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Difference Between 3G Handsets

Basically 3G handsets are based on HSDPA & WCDMA.
Here's the difference between HSDPA & WCDMA:-

WCDMA stands for Wideband Code Division Multiple Access.
HSDPA (High Speed Downlink Packet Access)

1. WCDMA is commonly referred to as 3G, while HSDPA is commonly referred to as 3.5G.

2. HSDPA provides much higher data rates compared to WCDMA.

3. HSDPA has lower latency times compared to WCDMA.

4. HSDPA has Fast Packet Scheduling and AMC, features that are absent in WCDMA.

5. HSDPA allowed speeds above 384kbps, the most notable of which is 3.6Mbps and 7.2Mbps,      Whereas WCDMA networks were only capable of reaching speeds of 384kbps
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