Digital lines provide faster and a more secure transmission as compared to the telephone lines. Digital transmission does not require the use of modems. Following are the different forms of digital lines:
- DDS (Digital Data Service)
- T1
- T3
- T4
- Switched 56
DDS sends data through a device called a Channel Service Unit/Data Service Unit (CSU/DSU). This device converts digital signals into a form that is part of the synchronous communications.
Note: With synchronous communication, bits are sent in a timed, controlled fashion. Transmission stops at the end of one frame and starts again with a new one.
T1 and T3 use point-to-point transmission that can transmit voice, data and video signals. T1 offers high data speeds and is the most widely used type of digital line. T3 is the highest capacity leased line service available.
Switched 56 is a digital dial-up service that requires a CSU/DSU to be installed with each computer on the network.