A preamble is a signal used in network communications to synchronize the transmission timing between two or more systems. Proper timing ensures that all systems are interpreting the start of the information transfer correctly. A preamble defines a specific series of transmission pulses that is understood by communicating systems to mean “someone is about to transmit data”. This ensures that systems receiving the information correctly interpret when the data transmission starts. The actual pulses used as a preamble vary depending on the network communication technology in use.