Half-duplex is a type of data transmission system in which transmitters and receivers are not able to simultaneously send and receive signals. In this system, data can only flow in one direction at a time, either from sender to receiver or vice versa. It is often used in cable systems to establish communications between two or more computers or devices.

In a half-duplex system, data is transmitted over a single cable, or a pair of twisted copper wires. This type of transmission is typically used in short-range applications, such as between two computers on a local area network (LAN). In this type of system, the two computers can communicate with each other, but only one at a time. The sender sends a signal, and the receiver receives the signal, but the two cannot send and receive signals simultaneously.

Half-duplex cable systems are typically used when cost or space constraints limit the use of a full-duplex system. This type of system is also useful when there is a need for a low-cost, low-complexity method of data transmission. Additionally, half-duplex cables can provide a way to extend the range of a network beyond what is possible with a full-duplex system.

Half-duplex systems are often used in digital communication applications, such as in radio broadcasts and in modems. However, they are also used in many other applications, such as in telephone systems, cellular networks, and digital television systems.

Although half-duplex systems are generally less expensive and require less complexity than full-duplex systems, they are not ideal for applications that require high data throughput or require simultaneous transmission and reception of data.