An optical signal detector monitoring circuit can include a current divider current mirror and a current multiplier current mirror. To enhance the response of the indexing system, it includes multiple routers, which it selects based on location relative to the reader. The video coding method also includes determining filter data items that are used to filter each of at least two of the prediction signal, the prediction error signal, and the reconstructed video signal; and coding the determined filter data items based on the cross correlations between the determined filter data items. If a deviation is detected, then the user is notified and calibration is failed. The unwelded ends are laser welded to the periphery at the flush surface to provide a unitary subassembly. A temperature responsive bi-metal element is coupled to the moveable element for moving the moveable element between the first position and the second position.