Abstract: Method and apparatus for the real time detection of the formation of ice on a surface in which a sensor having spaced electrodes along the surface is embedded in the surface for which detection is to be provided. Resistance between the electrodes is monitored and electrode temperature is monitored. When a sharp rise in resistance on the surface due to the presence of ice is detected at the same time that the surface temperature is at or below the freezing temperature of water, then a computer provides a signal to indicate the formation of ice.

Abstract: Special prompt character identifying control codes are inserted in teletext data for transmission to a teletext equipped receiver. The prompt character identifying codes are detected in the receiver and applied to a symbol converter which alters the prompt characters displayed on the receiver CRT to assure that all prompt characters displayed conform to character symbols actually available on the users teletext keyboard thereby avoiding user confusion as to the particular key-strokes required to access material identified in the teletext menu.