I know how data is saved in transistor and capacitor ,but how is it transported,especially in cable tv where many channels are sent simultaneously
The data is encoded before it is transmitted and decoded by the receiver. High data rates are required, but RF cables and fiber optic cable can easily support the data rates.
Basically, it sends a message in binary code A certain voltage represents 1 and another, usually lower, voltage represents a 0
Digital data is sent in many different ways. The simplest is a serial string of 1's and 0's, which are coded as two different voltage levels. The voltage varies between the two voltages at a high rate, say 1 MHz, and the receiver decodes that. RS232 is an example. Other serial standards are USB, which is much faster and more reliable than RS232. A more complicated method is as follows: The digital signal can be used to modulate an RF signal, and this is then decoded at the receiver. You can put many RF signals through the same wire if the signals are at different frequencies. Cable TV uses this to transmit hundreds of TV signals as well as phone and internet through one coax wire. The receiver acts similar to a radio receiver and tunes in the one signal (station) that it wants out of the many present, via tuned circuits (simplistically).
