The Precision Tone Generator (Model 177) is portable, battery-operated, and designed for use in fault location and pair identification operations. This unit is very useful when toning in high circuit noise or power influenced areas. The 577.5 Hz tone can be easily detected, while other tones cannot, when using any amplifier, tuned or filtered, to receive the 577.5 Hz tone. The -27 to +27 dBm variable output of the Model 177 allows the operator to adjust the signal level for each job application. The tone generator and test leads fit neatly in a durable, protective woven polyester carrying case with shoulder strap.