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.GBR File Extension

File Type	Gerber File
File Format	File
Common?	No
File Description	Industry-standard file format used for creating printed circuit board (PCB) designs; recognized by PCB manufacturing machines and contains instructions for drilling and milling the board; also includes information about the board's electrical connections.
Program(s) that open gbr files	Mac: Gerbv; gEDA Windows: Altium Designer; GraphiCode GC-Prevue; Pentalogix ViewMate; Pentalogix ViewMaster; SofTech DesignGateway Unix: gEDA

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http://www.fileinfo.com/extension/gbr