A centrifugal fan that includes an impeller having fan blades with notched tabs extending through slots in a pair of disc shaped base elements with the notches engaging the ends of the slots to secure the fan blades upon the impeller. The controller is programmed for controlling one or more external work operations associated with one or more utility devices. The method also includes providing the sensor analog voltage to the peak detecting circuit and detecting the peak voltage. The holster is securely attachable to the bicycle forks using a pair of conventional pipe clamps. Distributed and other operating systems, environments and architectures, such as, for example, those using tamper-resistant hardware-based processors, may establish security at each node. The amplifier can be configured according to at least a first gain configuration associated with a first gain value, and a second gain configuration associated with a second gain value.