Voice Infrastructure

A traditional cellular network is based on the fixed PSTN (Public Switched Telephone Network), but with some extra databases to deal with mobility. The equipment is analogous to switches, the devices at traditional telephone exchanges, which establish circuits whenever a call is made.

Mobile networks are relatively new compared to the fixed system—they date from around 1980, rather than 1900—so the switches they use tend to be more advanced. All switching is digital, even on G1 systems, which use an analog air link. All mobile phones use tone dialing, which represents digits by musical notes; none use pulse dialing, which sends a series of clicks instead and is still found on many fixed lines.

Though packet data is the hot ...

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