a Part 1 Notes to text Communications Channel 1) It may be defined by a physical wire that connects communicating devices, or by a radio, laser, or other radiated energy source that has no obvious physical presence连接通讯设备的物理导线、无线电波、激光或其它那 些无形的辐射能源,都可说成是信道。 注释:该句是复合句,主语指代 a communications channel;谓 语是 may be defined;其状语由两个并列的介词短语构成,分别 REby a physical wire, a radio, laser, M by other radiated energy source;定语从句 Ithat connects communicating devices]bfpa physical wire; that has no obvious physical presence则修饰 other radiated energy source。 2021/2/20 P22021/2/20 P.2 @ Part 1 Notes to Text 1) It may be defined by a physical wire that connects communicating devices, or by a radio, laser, or other radiated energy source that has no obvious physical presence. 连接通讯设备的物理导线、无线电波、激光或其它那 些无形的辐射能源，都可说成是信道。 注释：该句是复合句，主语it指代a communications channel；谓 语是may be defined; 其状语由两个并列的介词短语构成，分别 是by a physical wire，a radio, laser, 和by other radiated energy source；定语从句that connects communicating devices修饰a physical wire；that has no obvious physical presence则修饰other radiated energy source。 Communications Channel