This invention relates to a process for conducting equilibrium-limited reactions, such as esterification and alcoholysis reactions, that uses two reaction zones. The OCM 10 is a free-space optical device that includes a collimator assembly 15, a diffraction grating 20 and a mirror 22. In the power saving mode, the wireless terminal wakes up every listen interval and listen the beacon to check whether any buffered packet for it. A method for identifying the depth of insertion of a transluminal device into an artery or vein based on the presence of pressurized blood internal to the vessel and the absence of pressurized blood external to the vessel is also provided.