A system for supporting Voice over Internet Protocol, VOIP, and Circuit Switch,CS, telephone, comprising a terminal gateway device, a wireless broadband module and a Subscriber Line Interface Circuit,SLIC, wherein the wireless broadband module is adapted to perform network registration of a VOIP call, connection to a Wide Area Network, WAN, and establishment of a CS call and to complete transmission of a voice code stream between the terminal gateway device and a wireless broadband network; the terminal gateway device is adapted to determine whether a currently initiated call is a VOIP call or a CS call according to a received signal; if the currently initiated call is a VOIP call, to establish a Session Initiation Protocol, SIP, connection via the wireless broadband module, to convert a Pulse Code Modulation,PCM, line signal into a VOIP voice code stream, and to send the converted VOIP voice code stream to the wireless broadband network via the wireless broadband module or to convert a VOIP voice code stream from the wireless broadband module into a PCM line signal; if the currently initiated call is a CS call, to establish a CS connection via the wireless broadband module, converting a PCM line signal into a CS voice code stream, and to send the converted CS voice code stream to the wireless broadband network via the wireless broadband module or to convert a CS voice code stream from the wireless broadband module into a PCM line signal; characterized in that the SLIC is adapted for bidirectional transmission of a Serial Peripheral Interface,SPI, signal between a telephone and the terminal gateway device as well as bidirectional transmission of a PCM line signal between a telephone and the terminal gateway device, wherein the terminal gateway device comprises a SLIC drive module, a voice Digital Signal Processing,DSP, module, a Real-Time Transmission Protocol,RTP/ RTP Control Protocol,RTCP, module, a SIP module and a voice application module, wherein the SLIC drive module is adapted to detect a SPI signal coming from the SLIC, to determine whether the currently initiated call is a VOIP call or a CS call, to encode a PCM line signal into a VOIP or CS voice code stream corresponding to the type of the call, to send the encoded voice code stream to the voice DSP module, and to decode a VOIP voice code stream or CS voice code stream from the voice DSP module to a PCM line signal; the voice DSP module is adapted to compress and encapsulate an encoded voice stream to obtain a voice data packet, to send the voice data packet to the RTP/RTCP module in the case of a VOIP call or to the voice application module in the case of a CS call, and to unpack and decompress a voice data packet from the RTP/RTCP module or the voice application module to obtain a VOIP voice code stream or CS voice code stream; the RTP/RTCP module is adapted for real-time transmission control of a voice data packet over an IP network for a VOIP call and is adapted to send a voice data packet from the voice DSP module to the wireless broadband module via the voice application module and further to the IP network via the wireless broadband module, and to send a voice data packet received by the voice application module to the voice DSP module; the SIP module is adapted to create, modify and release a VOIP session; and the voice application module is adapted to identify a voice code stream coming from the wireless broadband module, to determine whether a currently initiated call is a VOIP call or CS call; if the currently initiated call is a VOIP call, to establish a connection between the terminal gateway device and the wireless broadband module through a Point-to-Point Protocol,PPP, and to send a received voice data packet to the RTP/RTCP module; if the currently initiated call is a CS call, to send a received voice code stream to the voice DSP module.