Devices and methods for determining analyte levels are described. The first electrical component exhibits a first temperature variable impedance and is positioned in thermal contact with a first switch having a second temperature variable impedance. by maintaining an inoperable block table that includes an entry for each inoperable PCM block and an address of a remapped PCM block. Upon receiving multiple incoming calls at about the same time, the apparatus can repeatedly output calling signals to corresponding communication terminals, without having multiple calling signal output apparatuses. The spool-shaped rollers may be molded of a rigid plastics material with each roller having end flanges to confine the synthetic sling.