Complex sentence: Long after they stopped being used for communications, spark gap transmitters were employed for radio jamming and are still used to generate high frequency voltage for welding arc initiation in gas tungsten arc welding.
Split into simpler sentences: Long after they stopped being used for communications, spark gap transmitters were employed for radio jamming. Spark gap oscillators are still used to generate high voltage high frequency voltage to initiate welding arcs for gas tungsten arc welding.