'1553' - description

1553: MIL-STD-1553 is military standard published by the United States Department of Defense that defines the mechanical, electrical and functional characteristics of a serial data bus. It was originally designed for use with military avionics, but has also become commonly used in spacecraft on-board data handling (OBDH) subsystems, both military and civil. It features a dual redundant balanced line physical layer, a (differential) network interface, time division multiplexing, half-duplex command/response protocol and up to 31 remote terminals (devices). It was first published as a U.S. Air Force standard in 1973, and was first used on the F-16 Fighting Falcon fighter aircraft. It is widely used now by all branches of the U.S. military and has been adopted by NATO as STANAG 3838 AVS. MIL-STD-1553 is being replaced on some newer U.S. designs by FireWire.[1]
Source: Wikipedia (http://en.wikipedia.org/wiki/MIL-STD-1553).