About a decade ago, when semiconductors for higher wattages were first marketed on a large scale, attempts were made to replace the conventional copper/iron ballast for gas discharge lamps by semiconductor circuits. It was thought that low power losses and small size were a great asset. Attempts to apply semiconductor circuits for current stabilization in the ballast failed, but for economic rather than technical reasons. The work did however result in a few specific uses. For example, where the normal 50/60 Hz a.c. mains is not available semiconductor ballasts can be used to advantage, as in trains and buses. For important secondary uses of the ballast which make the ballast cumbersome and expensive, such as igniting and re-igniting lamps, electronic circuits may be used.