it enters a system already at work

that most people never get to see.

The United States Postal Service processes

hundreds of millions of mail pieces every day.

The Postal Service delivers almost half the world's mail

to over a hundred and fifty million addresses,

through a network of thousnads of post offices.

These offices are supplied by a network of hundreds of

Processing and Distribution Centers around the nation.

The Postal Service separates mail into three categories:

letters, flats, and packages.

Small pieces of mail like letters, bills, and post cards

are all processed by the same set of machines.

Processing letters begins with culling,

or filtering out mail that cannot be handled by

machines down the line due to size, shape or weight.

Letters then enter the Advanced Facer-Canceller System.

This machine uses specialized cameras

to take pictures of envelopes as they speed by.

These pictures are used by the computer

to find the stamp,

locate the address,

read the handwriting,

and compare the address

against a database of known addresses.

It faces the letter in the right direction,

sprays it with a unique ID tag

and cancels the stamp with a postmark.

The letters are then transferred

to the Delivery Barcode Sorter.

Postal workers feed the letters

into this machine by hand.

This machine sorts letters into "delivery point sequence,"

or the order that postal carriers

will deliver them along their routes.

After letters are sorted,

they are moved to the loading dock.

Customers often bring large bundles of

magazines to distribution centers for processing.

The Postal Service refers to magazines,

catalogs, and similar items as "flats."

Large bundles of flats must be weighed and verified

before they are processed.

They are them taken to a preparation area.

There, they are separated and readied for processing.

After they are prepared,

bins of flats go into the Flats Sequencing System,

a machine the length of a football field.

The flats travel along a conveyor system to a feeder,

where they are removed from the bins

and sent one by one to the scanning system.

A high-speed camera captures image of flats

to identify their delivery addresses.

A computer interprets the scanned addresses

and sends sequencing information

to the machine's robotics system.

The flats are then sorted

into delivery order for postal carriers.

Sorted flats are then transferred to trays

and automatically loaded onto carts.

They are then moved to the loading dock.

Packages can be particularly difficult

to process be machine

because they come in a wide variety of sizes and shapes.

The Automated Package Processing System

is uniquely equipped to deal with this kind of mail.

Packages are spread out

as they moce along a series of belts and rollers.

As the packages enter the scanning and imaging tunnel,

the machine reads their addresses.

It determines the package dimensions...

and weight.

Checks for proper postage

and scans the barcode,

updating the package's tracking information.

The packages then travel along a conveyor,

before being kicked off into bins by destination.

Packages are then moved to the loading dock,

where they are loaded on to trucks

along with letters and flats going to the same post offices.

As morning approaches,

drivers deliver the sorted mail

to the appropriate post offices.

After the mail arrives,

postal workers separate it for pickup.

Carriers gather the sorted letters, flats, and packages

to take out on their routes.

Mail delivery connects people and businesses

all across the country.

Everyday technology keeps mail flowing

through this constantly moving network.

All systems...

at work.