Symmetric Digital Subscriber Line (SDSL)

Symmetric Digital Subscriber Line (SDSL) is an umbrella term that refers to a series of xDSL technologies that deliver broadband connectivity to the business or the residence over a single copper pair. The term symmetric refers to the fact that, unlike ADSL download and upload speeds are the same.

There are several versions that deliver different speeds:

  • ISDN Digital Subscriber Line (IDSL) - delivers equivalent bit rates as ISDN at 144 kbps
  • SDSL - delivers equivalent bit rates as a T1 connection at 1.554 Mbps
  • High-bit-rate Digital Subscriber Line (HDSL) - delivers 1.554 Mbps over either one pair or two pairs of copper
  • Single-pair High-speed Digital Subscriber Line (SHDSL) - delivers 5.696 Mbps per pair, over up to four pairs for a total exceeding 20 Mbps