A detector assembly for imaging a scene over a predetermined temperature range and a predetermined wavelength range including a central wavelength includes an imaging-sensor array, a plurality of focusing elements and a plurality of optical filtering elements. A valve is positioned in the dispensing system along the line of supply of the second fluid upstream of the mixing point, such valve being simultaneously actuated through application of positive andor negative pressure to allow the second fluid to flow through the valve. At least one surface of the negative lens has an aspheric shape. In at least one embodiment, the controller indirectly determines a state of the inductor current using at least one non-inductor-current signal. In IP mode, data service can share bandwidth with the mute frames of voice service, the system can coexist with different IP networks, and the control user planes are independent so as to simplify the developing procedure and reduce the maintaining cost.