unit 138 the number of devices in the chain is limited by the granularity of power sensing and power classes established e g under ieee 802 3af there are 4 classes 0 4 7 15 4 watts it is anticipated that higher levels of power will eventually be made available under ieee 802 3af and possibly finer granularity allowing more classes with three levels of delivered power available the present invention can be utilized to support a maximum of three devices each consuming four watts or less by decreasing the granularity of the current sensing more devices could be supported to share the total of 15 4 watts potential more on future systems the pse pd combination unit can for example include circuitry to provide functionality such as an ip camera a voip telephone a sensor and the like with the power for these functions supplied as inline power and accounted for as consumed power as discussed above three primary functional blocks of the pse pd combination unit are 1 the pd component 124 which acts as a pd power request unit to request power from a coupled pse based on predefined current limits drawn by the pd in the power classification stage these current limits are represented by resistance values in one embodiment of the invention by adjusting the prss 128 the power requested is changed usually reduced after a rejection once a power request is accepted the prss 128 stays in that state until a new power classification cycle is initiated typically upon reboot of a switch or an interruption in connectivity to the pse 126 the state of the prss 128 is representative of the power available to the pse pd combination unit 122 and a corresponding value is provided to the summation unit 134 2.