The disadvantage of having many point to point connections is that a lot of cable has to be used. The multiplexer is a practical communications product that saves cable. Multiplexers are used in pairs and a single multiplexer can replace up to 4 cables. The multiplexer creates up to 4 communication channels which can communicate independently of each other in full duplex, through Time Division Multiplexing (TDM). Multiplexing is possible with ordinary 4-wire cables or fiber optic cables. The multiplexer can be used as a component within a large network or within a network where a main computer must be accessed from several terminals, e.g. a hospital computer with terminals in different departments or an industrial process computer where the terminals are in the manufacturing plant. The data transmission distance between the multiplexors is up to 1 200 meters with copper wire (MX-16) and up to 3 500 meters with fiber optic cable (MM-61, MX-69). Speeds up to 115.2 kbit/s is possible with copper wire and up to 38.4 kbit/s with fiber optic cable.