Data can exist in both analog and digital forms. Digital data is transmitted as discrete signals using various components of communication systems like senders, receivers, transmission media, and protocols. Common transmission media include wired methods like twisted pair cables, coaxial cables, and fiber optic cables or wireless methods using radio waves, infrared, Bluetooth, or WiFi. The transmission speed depends on the type of channel used, with narrowband channels having lower speeds than broadband channels. Popular communication protocols for networks include TCP/IP, SPX/IPX, and X.25.