Simplex and Duplex Simplex and Duplex A communications network can provide many types of service. The most basic type of service is known as simplex. This service provides one-way communication. Examples of this type of service are TV distribution, and the transmission of burglar alarm messages.
Most networks transfer data in two directions and are known as duplex communications links.
This is known as broadcast transmission. In addition to broadcast, some networks also allow simultaneous transmission to a specific group of users, this is known as multicast transmission. An example of multicast transmission is the use of the IP network protocol to support packet video allowing remote participation in conferences across the Internet.