SDSL, Symmetric Digital Line Subscriber, is a type of DSL service. As one of a few different variations of DSL, SDSL connects through the phone line but offers different services and limitations. Having a Symmetric Digital Line Subscriber means that the connection uses a single line through the phone jack and offers the same upstream and downstream capabilities. With only one line, SDSL is a type of DSL that does not allow analog phone service. This means that you either will not have a phone service or you will need to use a digital or VoIP phone connection.
SDSL is one of the few types of DSL, along with Naked DSL, that does not require customers to have a phone service. SDSL does require a specific modem to convert the Internet connection and manage Internet speeds.
Other types of DSL
Along with SDSL, there are also VDSL and ADSL. Each of these DSL services connects differently and varies in what it can provide to customers.
SDSL vs. ADSL
ADSL, Asymmetric Digital Line Subscriber, is high speed DSL Internet with two different settings for upload and download speeds. Unlike SDSL, which has identical upload and download speeds, ADSL has different speed restrictions that often allow for higher download speeds. This is popular because most users require more download than upload speed. ADSL speeds vary. On average, your ADSL connection will have up to 5 Mbps. This service can provide simultaneous phone and Internet service.
SDSL vs. VDSL
VDSL, Very-high-speed Digital Line Subscriber, is the fastest DSL connection available. VDSL uses fiber-optic cables and supports both voice and data transmission. This service can be symmetric or asymmetric, based on your needs. VDSL can reach up to a little over 50 Mbps. This speed is based on your area and your Internet plan.