A sign display mountable over a top surface of a cubicle wall includes a sign holder having a frame and a depending post extending therefrom for carrying a sign. A paraboloidal trough reflector is positioned about a linear heating element to focus and concentrate radiant energy emitted from the heating element onto a thermal spreader. Second upper electrodes are formed in regions that do not overlie the buried electrodes. The first zone and the second zone are coupled to an electrically highly conductive layer.