The invention relates to a dressing material comprising a thermoplastic, the thermoplastic being applied to a first textile web and the thermoplastic containing a first microencapsulated dye. The signal inspection system comprises a signal capturing device, a determining module, a signal transforming device, and a processing module. Transistor drive circuitry controls conduction of the first and second transistor in a non-overlapping conduction operation. The paths ensure that signal charge generated across the entire width of the channel is collected together into regions of smaller area so that the likelihood of interaction with traps is reduced, and charge containment is maintained near the optimum for all signal levels up to the full well.