MSDSL (Multirate Symmetric DSL)
A variation of an earlier design full duplex (two pair) Symmetric DSL that provides for multiple data rates, allowing vendors to offer tiered pricing from the same equipment. Uses CAP encoding (discussed below) with interfaces to digital PBX systems. MSDSL can transmit on lines 29,000 ft long at a rate of 2,048 Kbps, on a single pair of copper wires.
HDSL (High Bit-Rate DSL)
A synchronous design (same upstream and downstream bandwidth) that is usually used to transmit data between corporate sites. Capacity approaches that of a T1 telephone line, using two or three twisted pairs of wire. For distances less than 12,000 ft from central station: 2.048 Mbps. For distances less than 15,000 ft from central station: 1.54 Mbps.
HDSL2, a newer standard, can transmit on lines 29,000 ft long at a rate of 2,304 Kbps, on a single pair of copper wires.
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