This part of IEC 61156 describes the cables intended primarily for horizontal floor wiring as defined in ISO/IEC 11801. It covers individually screened, common screened and unscreened pairs or quads (see Annex A). The transmission characteristics and the frequency range (see Table 1) of the cables are specified at 20 °C. These cables can be used for various communication channels which use as many as four pairs simultaneously. In this sense, this sectional specification provides the cable characteristics required by system developers to evaluate new systems. The cables covered by this standard are intended to operate with voltages and currents normally encountered in communication systems. While these cables are not intended to be used in conjunction with low impedance sources, for example, the electric power supplies of public utility mains, they are intended to be used to support the delivery of low voltage and power applications such as IEEE 802.3af (Power over Ethernet) and IEEE 802.3at (Power over Ethernet Plus).