A telephone operator signal analysis and manipulation subsystem is configured to be interfaced with various signal transport paths of inputoutput devices of the operator’s workstation. The method comprises providing a flexural rigidity distribution of the region, providing a Young’s modulus distribution of the region, and modifying the flexural rigidity distribution with the Young’s modulus distribution to obtain an equivalent elastic thickness distribution of the region indicative of the structure thereof. Live, attenuated IB viruses of the invention may be produced by serial passaging of an IB-QX-like virus. The authentication memory 332 can be accessed only by external devices which have been affirmatively authenticated. A filter portion is fitted within the filter housing portion. The dental apparatus includes LEDs mounted on the cheek retractors.