Cambridge O Level Computer Science · Syllabus 2210 · Data Transmission
Simplex
What is Simplex?
Simplex transmission is data transmission in one direction only, from sender to receiver, with no return channel. A keyboard sending keystrokes to a computer is the standard example; half-duplex and full-duplex add a return direction.
This definition is part of the Data Transmission chapter in Cambridge O Level Computer Science.
Simplex in context
These three describe which directions data is permitted to travel, and whether both directions can be active at the same moment. In simplex transmission, data travels in one direction only. In half-duplex transmission, data can travel in both directions, but not at the same time. In full-duplex transmission, data can travel in both directions at the same time. Two words decide every question in this area: direction and simultaneously.
A scenario question never wants a memorised list. It wants you to find the features of the situation that decide the answer, and then say which property of the method each of those features points to. Two independent questions have to be answered every time: how do the bits travel? (serial or parallel) and which directions are needed, and when? (simplex, half-duplex or full-duplex). Answering only one of them leaves half the marks on the table.
Questions students ask about Simplex
What is the difference between simplex, half-duplex and full-duplex transmission?
These describe which directions data may travel and whether both directions can be active at once. Simplex transmission sends data in one direction only, such as a keyboard sending keystrokes to a computer. Half-duplex allows data both ways, but not at the same time. Full-duplex allows data to travel in both directions at the same time, so both devices can send and receive simultaneously. The two words that decide every question here are direction and simultaneously.