Advantages of digital over analog transmission

Digital transmission sends information as discrete (binary) levels, while analog transmission sends a continuously varying signal. Digital has these advantages:

1. Noise immunity: the receiver only decides between two levels (0 or 1), so small noise does not change the data. Analog noise adds directly to the signal and cannot be removed.
2. Regeneration: a repeater can rebuild a clean pulse, so noise does not accumulate over long distances. Analog amplifiers amplify noise along with the signal.
3. Error detection and correction: parity, CRC and error-correcting codes can detect and fix errors.
4. Multiplexing: many channels share one link easily by TDM, and different data types (voice, data, video) are carried in the same format.
5. Security: data can be encrypted and compressed easily.
6. Processing and storage: the data is already in a form that computers and microprocessors can store and process, and digital hardware is cheap and compact (ICs).
7. Better quality: signal quality does not degrade with distance as long as the bit error rate is low.

The main cost is larger bandwidth for the same information and the need for A/D and D/A conversion, but the advantages above usually outweigh this.