A technique for estimating the location of a wireless terminal at an unknown location in a geographic region is disclosed. The circuit compares the time derivative of a voltage signal indicative of the RF output power to the time derivative of a control voltage signal for the RF power amplifier. The present invention is also directed to an assay kit and a reagent useful for carrying out the steps of the above method. The shielding components are wider than the collimating components but the collimating components have a greater height. For example, an apparatus in accordance with an embodiment of the invention includes a detector to determine whether an incoming input is a wireless communication signal intended for reception, based on an operation applied to a cross-correlation value and an auto-correlation value. By visualizing the state of a driving system in a vacuum, a vacuum valve, a vacuum state and a state of an electro-optic system on a screen, the device state in a vacuum may be grasped.