The single panel is on the most basic PCB, the parts are concentrated on one side, and the wires are concentrated on the other side (the patch elements are the same side as the wires, and the plug-in devices are on the other side). Since the wire only appears on one side, this PCB is called a single-sided. Because single-panel has many strict restrictions on the design line (because there is only one side, the wiring can not cross and must be around the path), so only the early circuit used this type of board.