What is MIL-STD-1553 and how is it used in military avionics?

MIL-STD-1553 is the standard data bus for military avionics, defining electrical, protocol, and data characteristics. Features: 1 MHz data rate (dual redundant buses), Command/response protocol with single bus controller, Up to 31 remote terminals per bus, Deterministic timing, and High reliability through transformer coupling. Message structure: Command word, data words (up to 32), status word. The bus controller schedules all transactions. Widely used in fighter aircraft, helicopters, missiles, and space systems. Mature, reliable technology but bandwidth limited. Newer systems use higher-speed networks (Fibre Channel, Ethernet) while 1553 remains for legacy systems and where reliability is paramount. Test equipment and standards well established.