and 11 however since backflow of ss signals to the commercial electric power line 101 are prevented by means of the blocking filters 4 the confidentiality of the ss communication signals is not compromised via the commercial electric power line 101 conversely since noise transmitted along the commercial electric power line 101 from machine tools and other load devices is cut off by the blocking filters 4 and not transmitted to the alternating current power supply lines for communication 10 b or 11 it is easy to isolate just the ss signals enabling the maintenance of stable communication quality consequently individual noise filters are not required on each machine tool in the present embodiment the plugs for terminal connection 7 and plug sockets for terminal connection 6 have the same shapes as the plug socket 104 and electrical plugs 5 a and 5 b respectively however it is permissible for the plugs for terminal connection 7 and the plug sockets for terminal connection 6 into which the plugs for terminal connection are plugged to have different dimensions from items connected to the commercial electric power line 101 making the sockets and plugs in different shapes or sizes helps the installer distinguish between connections to the alternating current power supply lines for communications 10 and 11 and connections to the commercial electric power line 101 preventing mistaken connections moreover the above mentioned embodiment was described with connections between each load device and the input output portion of the spread spectrum communication terminal apparatus via a wired communication cable but if the transmission environment is one in which ss signals will not become confused it is permissible for.