A planar carbon segment commutator assembly made by forming an annular conductor substrate with an annular front projection extending integrally and axially from a front surface of the substrate. A correction signal is used for compensating for a dc offset in a data signal containing at least part of the information to be transmitted. A method of coating the firebox chamber includes preparing the surface of the tubesrefractory walls, preparing the coating, and applying the coating to the surface. In some embodiments, the blower has a snap-fit circuit board, containment system for mounting the motor, one or more vanes for directing fluid flow, shrouded impeller, andor integrated connector.