The Kidde-Fenwal KS-PS is compatible with the DS-PS base, so you won’t need to replace the base if it’s still in good condition. To install the KS-PS, simply remove the old DS-PS head from the base by twisting it counterclockwise and then install the KS-PS head by twisting it clockwise onto the existing base. Make sure to test the new detector after installation to ensure proper functionality. If you have any further questions, feel free to ask!