Single-Pair High-Speed Digital Subscriber Line (SHDSL)

A single-pair high-speed digital subscriber line (SHDSL) is a type of symmetric digital subscriber line (SDSL) that has symmetric upload and download speeds over conventional copper telephone lines, which is faster than what a conventional voiceband modem can provide. SHDSL uses trellis-coded pulse-amplitude modulation (TC-PAM) that operates at frequencies that encompass those used by analog voice POTS (plain old telephone service), meaning that a DSL splitter or frequency splitter cannot separate analog voice and data.