Twisted-pair wiring, when required by devices, is designed to eliminate external interference common to the wire pairs. Since the pairs are twisted together, this external "noise" is equally distributed onto the wires. The sending and receiving circuitry is expecting that these twisted pairs are used as a pair. If not properly connected as a pair, the noise cannot be rejected and could cause equipment dysfunction. 

Please pay attention to the colour coding on twisted pair cable, as the similar colours indicate the combined twisted wires. These are normally coded as a solid colour and the same solid colour with white. 

An example connection would be the substation ports on the N-8400RS substation interface.