In telecommunications, transmission (abbreviation: Tx) is the process of sending and propagating an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless. Transmission technologies and schemes typically refer to physical layer protocol duties such as modulation, demodulation, line coding, equalization, error control, bit synchronization and multiplexing, but the term may also involve higher-layer protocol duties, for example, digitizing an analog message signal, and source coding (compression).
Transmission of a digital message, or of a digitized analog signal, is known as data transmission or digital communication.
One transmission is the sending of a signal with limited duration, for example a block or packet of data, a phone call, or an email.
The converse of transmission is reception (abbreviation: Rx).