What is SDSL?
SDSL is the type of DSL but it support more data rate over the copper phone line and have same data rates for upstream and downstream. SDSL supports the data rates up to 3mbs. SDSL works by transferring digital pulses in the high-frequency region of copper wires and cannot work at the same time with voice connections on the same wires. SDSL also used the special SDSL modem.
SDSL was one of the earliest forms of DSL, requires pair of copper or phone lines and its cost is relatively more expensive than the normal ADSL.