The PP-20-SH Start-to-High Power Pack is ideal for certain types of HID Bi-Level lighting control. Upon initial power-up, the relay inside the PP-20-SH automatically closes bringing the HID Lamp to full On condition for up to 20 minutes. Check with Lamp manufacturer, typical initial start-to-high time is 15 to 20 minutes. Common application is using a Photocell (see CM-PC technical data) to Dim the HID lights during sunny periods. HID fixtures must be Bi-Level, when interfacing low voltage occupancy sensors to dim when area is unoccupied.