An image forming apparatus includes a PTC and a toner concentration sensor that are disposed adjacent to and downstream of a fourth image forming unit. A wide variety of modified substrates may be employed which provide either discrete or non-discrete sites for accommodating the microspheres in either random or patterned distributions. The content of the crucible is melted resulting in incorporation of the dopant in the molten material bath. A resource selector, supplied with the channel information 1SCI1 to NSCIN and the relative position information SRP, determines the assignment of resources to the first to Nth terminals and outputs the resource assignment information SRA.