An electrical adaptor (100) includes a first connection assembly (2) having a first printed circuit board (20), a first connector (21) mounted to a front segment of the first printed circuit board, a first variable resistor (24) mounted to a rear segment of the first printed circuit; a second connection assembly (3) having a second printed circuit board (30), a second connector (31) mounted to a front segment of the second printed circuit board, a second variable resistor (34) mounted to a rear segment of the first printed circuit board; a cover member (1, 6) enclosing the first connection assembly and the second connection assembly therein; and wherein the first printed circuit board and the second printed circuit board are disposed at different levels and partially overlapping each other.