Why do EDI and Barcodes works with ought power source and they still Sends signal that includes information about the inventory item it is attached to:

 Electronic Data Interchange (EDI) environment require bar coding to be the bridge which links transaction sets with actual cartons.                                                                                                         

Barcode DOES'NT send any signal.A barcode essentially is a way to 

encode information in a visual pattern that a machine can read. The combination of black and white bars (elements) represents different text characters which follows a set algorithm for that barcode type. If you change the sequence of elements you get different text. 

A barcode scanner picks up the alternating black and white elements 

of the barcode which follow a specific algorithm that is turned into a corresponding text string by the scanner. This information is then sent over to your computer by the scanner no different than a standard keyboard does. This string of text will populate where ever your cursor is on screen at that time.

Here's how they do it.   

For the sake of this simple example, let's assume that barcodes are simple on-off, binary patterns with each black line corresponding to a one and each white line a zero. (We've already seen that real barcodes are more sophisticated than this, but let's keep things simple.)

1.Scanning head shines LED or laser light onto barcode.

2.Light reflects back off barcode into a light-detecting electronic component called a photoelectric cell. White areas of the barcode reflect most light; black areas reflect least.

3.As the scanner moves past the barcode, the cell generates a pattern of on-off pulses that correspond to the black and white stripes. So for the code shown here ("black black black white black white black black"), the cell would be "off off off on off on off off."

4.An electronic circuit attached to the scanner converts these on-of pulses into binary digits (zeros and ones).

5.The binary digits are sent to a computer attached to the scanner, which detects the code as  .

Cheers!

Thanks a lot MR. Mohammad for your question. But I would like to do a little correction to your question before answering it. I suggest the question should be like this: 

How Barcode works without power source and it is still readable! That is, its included information about the inventory item it is attached to can read with some reader?

Now, we all know that the barcode is nothing but a way of coding information whithin a small area using those different thick lines to represent the behind information. As you may know barcodes can be printed on any lazer (or similar quality) printer. It prints like any characters on any white paper.

What the reader do is just scanning the barcode (reading it) and then converting it to the corresponding information. By sure to do reading a barcode, we should use the correct reader and it should be having a source of power in it (like a battery) or it should  be connected to a host PC.

EDI and Barcodes Takes it's power source from the connected Host Machine:

As an example:

USB Bracode Connect to the PC via usb cable which supply5V upto2A with usb3.1 Port

as a simple example when you connect your mobile to your PC it start charging and you can also transfer files via Data connection :)

Hope it's clear answer for you.