Question:So does that mean that you can only every send a number 1 or 0 via the digital signal?
Digital signals consist of binary codes. A binary number is made of a series of 1's and 0's.
The meaning of a binary code must be agreed between the sender and the receiver.
For instance the binary code 101001101011 (shwon below) could tell a television to turn to channel 18.
Notice how the code at the top is transformed into 1's and 0's. Also notice that a double width 'off' level means 00, a 0 signal value followed by a second 0 value.