mechanical items, 216 lines to carry fluids and gases, and 121 internal and external electrical cables using six miles of wire were installed in the Unity node. The primary structure of Unity is constructed of aluminium. During the space station construction, a crew member placed two speed limit signs on the hatch (leading into the FGB) in 2003, noting the orbital velocity in mph and km/h. Prior to its launch aboard Endeavour, conical Pressurized Mating Adapters (PMAs) were attached to the aft and forward berthing mechanisms of Unity. Unity and the two mating adapters together weighed about . The adapters allow the docking systems used by the Space Shuttle and by Russian modules to attach to the node's hatches and berthing mechanisms. PMA-1 now permanently attaches Unity to Zarya, while PMA-2 provided a Shuttle docking port. Attached to the exterior of PMA-1 are computers, or multiplexer-demultiplexers (MDMs), which provided early command and control of Unity. Unity also is outfitted with an early communications system that allows data, voice and low data rate video with Mission Control Houston, to supplement Russian communications systems during the early station assembly activities. PMA-3 was attached to Unitys nadir berthing mechanism by the crew of STS-92. Other nodes The two remaining station connecting modules, or nodes, were manufactured in Italy by Alenia Aerospazio, as part of an agreement between NASA and the European Space Agency (ESA). Harmony (also known as Node 2) and Tranquility (also known as Node 3) are slightly longer than Unity, measuring almost long in total. In addition to their six berthing ports, each can hold eight International Standard Payload Racks (ISPRs). Unity, in comparison, holds just four ISPRs. ESA built Nodes 2 and 3 as partial payment for the launch aboard the Shuttle of the Columbus'' laboratory module, and other ESA equipment. References External links NASA Facts: Unity Connecting Module: cornerstone for a Home in Orbit NASA, January 1999 Expedition 15 - Tour of the Unity Node filmed in July 2007 by Clayton Anderson Components of the International Space Station Spacecraft launched in 1998