SDSL. It's only four little letters, but what a difference those four letters can make for an emerging business. SDSL is a high speed Internet access service that offers up to 30 times the speed of standard dial-up access. Symmetric Digital Subscriber Line (SDSL) is the latest high speed technology that uses your existing copper telephone wires to provide high speed Internet access at equal uploading and downloading speeds. Our SDSL takes existing voice cable that connects customers' premises to the phone company's central office (CO) and turns the line into a high speed digital link. SDSL is the perfect solution for small- to medium-sized businesses and home offices.