Greenlee 801K Signal Generator and Trace Tone Set for tracing and identifying cables.  Greenlee 801K is one of the best tone and probe kits on the market.  This classic tone and trace kit comes with a filter probe, one that eliminated electric or AC hum (noise).  This special feature enables technicians to identify cables or wire that are close to electrical lines or electronic equipment, when regular tone and probe kit does not produce clear signal.  Greenlee 801K has been a standard tone and probe set at all telecom companies for many years.