A panel for free access to a signal cable (66, 68) and a power cable (70) is installed on the floor (4) of an office room and forms a network of signal cables in an office. The posts (40) of this panel are mounted onthefloor(4). A floor plate (12) is secured to the upper ends of the posts (40). A rack plate (32) is arranged between the floor plate (12) and the floor (4), and the rack plate (32) is secured to the posts. The height of the floor plate and the rack plate is adjusted by adjusting the engaging position by rotating a leg (52) to be engaged with the threaded holes (48) of the posts (40). The floor plates are composed of a plate made of glass, reinforced cement (82) mixed with foamable styrol or an aluminium honeycomb structure (22). The rack plate (32) is composed of a transparent polypropylene plate. Further, the surface ofthefloorplate (12) is covered with a surface material (14) such as a carpet. The signal cables are arranged in the space between the floor plates (12, 80) and the rack plates (32). The power cables are arranged in the space between the rack plates (32) and the floor (4). Electronic components (64) are mounted on the rack plates (32). Therefore, the power cables (70), the signal cables (66, 68) and the other electronic components (64) are completely isolated from each other, and the modification of the layout of office automation equipment can be readily carried out by an authorized person.