used to represent a wide variation of DSL technologies. Here's a quick guide to the most common terms you'll encounter.
High-Bit-Rate Digital Subscriber Line (HDSL) has been around the longest. It provides full-duplex T1 (1.544-Mbps) or E1 (2.048-Mbps) data transmission across existing twisted-pair copper without repeaters. By using the existing copper infrastructure, you can implement HDSL systems quickly.
Symmetric Digital Subscriber Line (SDSL) provides symmetric bidirectional variable-rate communications and voice on a single phone line. It transmits data at 160 Kbps to 2084 Mbps. This technology is suitable for applications that require a symmetric data rate.
Asymmetric Digital Subscriber Line (ADSL) provides three separate channels over the same phone line. The asymmetry is based on an approximate 10-to-1 ratio in the downstream-to-upstream data rates -- appropriate for high-speed Internet or m
ultimedia access. Phone conversations are carried on one channel, downstream data from the service provider to the user is transferred on another line, and upstream data from the user to the service provider runs in the third channel.
Very High-Bit-Rate Digital Subscriber Line (VDSL) simply means your data rate can increase because you're closer to the central office. Data rates of 13 Mbps at 5000 feet from the central office, 26 Mbps at 3000 feet, and 51 Mbps at 1000 feet are possible.
The "x" in xDSL
