As voice communications is the primary media of communication for human being, it plays a very important role from public switched telephone network to the third generation mobile communications.
No smoking is allowed inside the classroom. Mobile phones, pagers and other electronic communications must be switched off.
课室内不准吸烟。学员必须关掉所有手提电话、传呼机及其他响闹仪器。
3
The limited transmission rate available on the Public switched telephone network (PSTN) and on wireless networks presents a significant challenge to digital video communications.