CodeGate is a special button on the back of the scanner. When the laser lines up with 
the barcode you press the button and the scanner reads just that single barcode. 

In contrast the non Codegate version scans the first barcode it sees. 

If you have ever tried to pick out a single barcode on a sheet of closely printed 
codes, you will realise just how useful that can be.  

The CodeGate switch can be disabled and the scanner then acts exactly like the 
non Codegate version.