Sound recording device applied to PSTN (public switched telephone network)

The utility model relates to a sound recording device applied to a PSTN (public switched telephone network). The sound recording device comprises an embedded microprocessor, an analog trunk interface circuit, a storage device and a memory, wherein the analog trunk interface circuit, the storage device and the memory are connected with the embedded microprocessor, the analog trunk interface circuit comprises a codec, a telephone line interface module and an analog trunk interface, the analog trunk interface is connected with the codec and the embedded microprocessor through the telephone line interface module, and the codec is further connected with the embedded microprocessor. The sound recording device adopting the structure can pass through the analog trunk interface and get a bypass and an ordinary telephone to be further connected into an analog user interface of the same PSTN, thereby expanding an ordinary telephone system, realizing the functions of recording sound during conversion and playing the reco