One picture holds both meanings: a programme turned into a stream of numbers, carried away, and put back together at the other end. You can stand at either end of that line. Stand at the sending end and the words name the whole way of doing it. Stand in the living room and they name the box that reads the numbers and gives you back a picture.
One branch
同一條訊號線的兩端：做法與機器
兩個意思共用同一個畫面，只是站的位置不同：一個在訊號送出去的那一頭，一個在訊號被還原的那一頭。
noun · B1
A way of sending and receiving television programmes as digital signals instead of the older analogue ones. The signal can reach a home through the air, through a cable, or from a satellite dish.
數位電視（訊號系統）