HUM & NOISE IN RACK SYSTEMS... Usual mounting of 19" equipment in a rack system results in contact between the devices through the rack rails. This creates ground loops - the most common cause of hum and noise. The unique Humfrees mounting system interrupts these groundloops by isolating the 19" units from the rails and from each other. Scarring and scratching of the front panel by the mounting screws is also eliminated. HUMFREES - QUICK & EASY INSTALLATION! 1. Pull the unit out of the rack 5 cm. There is normally no need to disconnect the cables. 2. Bend the Humfrees Insulating Parts (4 x) around the corners of the front panel from the sides. 3. Reinstall the unit with the Humfrees Screws (4 x M6). For M5 or Inch based rack systems: Use your normal screws in combination with the Humfrees Adapters (4 x). Note: Adjacent rackmount units must not touch each other anywhere along the surface of their chassis.