This dual-head version of the Model 67200 (described above) is used for end-marking wires with long strip lengths and for applications that require printing two marks at a time, with the last character of the second mark located more than 3.5″ (88mm) from the first character of the first mark Spark Tester The Model 64055 high frequency sine wave spark tester is used in line with a marking machine to check the integrity of the wire insulation. If the insulation fails the spark test, the marking machine stops and a fault light turns on.