A field case housing has a substantially cylindrical wall segment, an end segment and a flange all having a substantially constant wall thickness. Also described is a recombinant pectin methyl esterase. The voice exchange is capable of exchanging voice signals between a switched circuit network and a packet based network. Each of the at least one spring-arms extending from an inside edge of the at least one aperture and operable to couple the heat sink to the at least one package.