Television audio signal encoders include a matrix that sums a left channel audio signal and a right channel audio signal to produce a sum signal. Radiation curable component is polymerizable upon exposure to electromagnetic radiation and comprises at least two functional groups comprising at least one bond activatable with electromagnetic radiation. The system provides visual alert for different conditions if food products are in unsafe status. The protective metal line has a resistance higher than that of the word-line. Additionally, new input devices and telepresence devices are easily added to the system and are frequently interchangeable.