The 7.5 VDC 1 amp Power Supply is recommended for programming SX chips. Please note that Parallax BASIC Stamp® Starter Kits DO NOT include a power supply. Each BASIC Stamp Starter kit page includes a link to the recommended power supply below the product description in the "Related Products" section. Please email support@parallax.com if you have any questions regarding the proper power supply for your project.
Resources: Power Supply Recommendation Chart