storage unit 30 may be a computer a smart media card a secure digital card or a flash card the storage unit 30 stores computerized codes of a marking system 10 at least one pcb layout 50 and a name file 60 the name file 60 records names of to be checked signal transmission lines the marking system 10 includes various software components and or a set of instructions which may be implemented by the processor 20 to automatically determine to be checked signal transmission lines according to the name file 60 and automatically mark the determined to be checked signal transmission lines fig2 is a block diagram of the function modules of the marking system 10 in the computing device 100 of fig1 in one embodiment the marking system 10 includes a reading module 12 a determining module 13 and a marking module 14 the reading module 12 includes various software components and or set of instructions which may be implemented by the processor 20 to read the names of to be checked signal transmission lines in the name file 60 the determining module 13 includes various software components and or a set of instructions which may be implemented by the processor 20 to determine the to be checked signal transmission lines in a pcb layout displayed on the display unit 40 according to the read names the marking module 14 includes various software components and or a set of instructions which may be implemented by the processor 20.