spandsp: spandsp (DSP library for telephony) spandsp: SpanDSP is a library of DSP functions for telephony, in the 8000 spandsp: sample per second world of E1s, T1s, and higher order PCM channels. spandsp: It contains low level functions, such as basic filters. It also spandsp: contains higher level functions, such as cadenced supervisory tone spandsp: detection, and a complete software FAX machine. spandsp: The software has been designed to avoid intellectual property issues, spandsp: using mature techniques where all relevant patents have expired. spandsp: See the file DueDiligence for important information about these spandsp: intellectual property issues. spandsp: https://www.soft-switch.org/