installation, repair and maintenance of submarine cables, aerial power transmission wire, communication equipment for control in buildings, telecommunication systems, telecommunication facilities, data communication facilities, computer systems; building construction; construction of communication plants; installation and repair of telephone sets and telephone wire; underground construction; rental and leasing of construction equipment, civil engineering machinery, earth moving equipment and excavators; providing information relating to construction; consultation and supervision in the field of construction and civil engineering works; inspection and maintenance of electrical facilities installed in buildings, and of building facilities; disinfecting telephone sets