This paper mainly researches the modulation and demodulation protocol of the H.324 communication protocol,and designs the modem software drivers based on the protocol. At last videophones can communicate on the PSTN.

• 324通信协议中的调制解调协议，并基于该协议对底层Modem软件驱动程序进行开发，最终实现了可视电话终端在公共交换电话网(PSTN)上互通。