Provides characteristics for: half-connections with digital interfaces; digital interfaces (Type KD, LD and MD); input and output connections with digital interfaces. These characteristics are given in accordance with definitions in I-ETS 300 003, especially in figures 1 and 3. Clause 5 of this I-ETS gives detailed transmission characteristics of the digital interface ports. Subclause 5.3 deals with the requirements for transmission characteristics of the half-connections between the PABX test points and the digital interfaces.