Scanlines I think. If so:
1. Make a new 3x3 file
2. Zoom into it and using the pencil tool on block mode, make 3 lines going in any direction.
3. Edit > Define Pattern
4. Then you go to your sig, Layer > New Fill Layer > Pattern > Choose the lines you made then your done.
(Also you might want to change some of the opacity to lighten it up

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