由Protel2004产生的Gerber文件各层扩展名与PCB原来各层对应关系表:

Layer : File extension
-------------------------
顶层Top (copper) Layer : .GTL
底层Bottom (copper) Layer : .GBL
中间信号层Mid Layer 1, 2, ... , 30 : .G1, .G2, ... , .G30
内电层Internal Plane Layer 1, 2, ... , 16 : .GP1, .GP2, ... , .GP16
顶丝印层Top Overlay : .GTO
底丝印层Bottom Overlay : .GBO
顶掩膜层Top Paste Mask : .GTP
底掩膜层Bottom Paste Mask : .GBP
Top Solder Mask : .GTS
Bottom Solder Mask : .GBS
Keep-Out Layer : .GKO
Mechanical Layer 1, 2, ... , 16 : .GM1, .GM2, ... , .GM16

Top Pad Master : .GPT
Bottom Pad Master : .GPB

Drill Drawing, Top Layer - Bottom Layer (Through Hole) : .GD1
Drill Drawing, other Drill (Layer) Pairs : .GD2, .GD3, ...

Drill Guide, Top Layer - Bottom Layer (Through Hole) : .GG1
Drill Guide, other Drill (Layer) Pairs : .GG2, .GG3, ...