Two-bus transmission device

The invention discloses a two-bus transmission device. The two-bus transmission device comprises a first bus, a second bus, a switchboard and at least one terminal, wherein the switchboard comprises a first return code detection circuit, a second return code detection circuit, a code sending control circuit, a first switch circuit, a second switch circuit, a direct-current power supply, a first capacitor, a switchboard transformer and a switchboard audio processing circuit; the terminal comprises a terminal decoding/code returning circuit, a terminal power supply circuit, a terminal transformer and a terminal audio processing circuit; the switchboard transformer is used for converting a first single-end audio signal transmitted by the switchboard audio processing circuit into a first differential signal to be transmitted; and the terminal transformer is used for converting a second single-end audio signal transmitted by the terminal audio processing circuit into a second differential signal to be transmitted