This paper proposes design criteria for the crosstalk interference between digital line systems operating in multipair cable, with plesiochronous and synchronous network configurations. Existing solutions are shown to be appropriate in some cases, in some other cases to be based on imperfect design criteria, and in other cases, such as the plesiochronous case, to be absent. For engineering purposes, the application of a 3 dB additional margin to the design criterion based on the classical solution should be adequate for practical application in the network.