A host signal processor (HSP) modem has a software interface between HSP modem hardware and native audio hardware in a host computer. No hard wire connections between modem hardware and audio hardware are required for synchronization. Instead, a software clock recovery system matches a transfer rate...http://www.google.fr/patents/US5940459?utm_source=gb-gplus-shareBrevet US5940459 - Host signal processor modem and telephone
