A system to monitor the entry and exit of individuals from a facility and to identify individuals who have entered the facility and not indicated safe departure from the facility by reporting to an emergency reporting area and activating the system with an identification card. In one embodiment, the method includes inducing a substantially minimum or a substantially maximum frequency output from a voltage-controlled oscillator, and configuring a divider with a corresponding dividing ratio. Such non-halogenated rubber compound includes a blend of rubbery polymers in combination with aluminum trihydrate, which is a fire retardant, and optionally a phosphate plasticizer, which can provide the rubber compound with a more desirable workability. The improvement comprises: a hub defining the threaded bore; an annular element providing the abrasive material, the annular element having a central primary aperture aligned with the threaded bore in the hub to provide access to the bore by said spindle in use; and elements mechanically securing the hub to the annular element, for co-rotation.