| 摘要 |
PROBLEM TO BE SOLVED: To allow for transmission and reception of audio, video, and data signal by a transmission line consisting of two lines, while insulating between apparatuses easily without using a transformer.SOLUTION: Connection of a collective entrance unit 1 and a controller 3, and connection of a room unit 2 and the controller 3 are carried out by a transmission line consisting of two lines. The collective entrance unit 1 and room unit 2 include interface circuits 11, 21 for transmitting an audio signal and a data signal while arranging in the same first frequency band B1, and transmitting a video signal while arranging in a high second frequency band B2 different from the first frequency band B1. An audio signal, a data signal and a video signal are transmitted on a transmission line L. |
