NSI-63

NSI-63 is a railway signaling system used for interlocking on the Norwegian railway network. It is based on relays and was developed by Norsk Signal Industri for the Norwegian State Railways (NSB) during the early 1960s. The systems are installed at railway stations and passing loops and consist of single relays built form drawings. The system is simple, robust and economical for smaller stations on single-track railways. The system makes use of track circuits for train detection.

NSB-63 was based on NSB-EB, the very first automatic interlocking system used in Norway. NSB-63 is the most common system used in Norway, with about 220 installed interlockings belonging to the Norwegian National Rail Administration. This is more than the combined number of other interlocking systems. About 140 of the systems were installed during the 1960s, with about 80 installed during the 1970s. NSB later developed a series of modified versions of NSI-63, which were installed up until the 1990s. The first development was NSI-63/PLS, which used programmable logic controllers (PLC) instead of telephone relays. Other variations include NSB-78 and NSB-84, which have about 25 and 10 installed units, respectively.

The most extensive redevelopment of NSI-63 is NSB-87. It was developed to be installed on the Røros Line, including all stations between Hamar and Røros, and selected stations on the Nordland Line. It was designed to only work at the simplest stations, and lacks some of the more advanced features in NSI-63. NSB-87 was developed by SattControl, now part of ABB Group, who made the computer and communication systems, based on PLC. The National Rail Administration made the relay circuits and the software. The design of NSB-87 included a simplification of the NSI-63 design, in particular to reduce costs.

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