A compensation circuit compensates for the variation in the internal resistance of a multi-track inductor over temperature. The computer-telephony integrated user console further includes an intelligent integrated keyboard which includes at least one programmable display key. The testing box includes a plurality of holders ; the holders define a datum plane. The reference stage works in conjunction with the second stage to control the output of the second stage. The second web of panel material 2 is guided by a guide device 18 to be folded after being heat sealed so that a second folded portion should be formed in the second web of panel material.