Routing indicator

1. A group of letters assigned to indicate: (a) the geographic location of a station; (b) a fixed headquarters of a command, activity, or unit at a geographic location; and (c) the general location of a tape relay or tributary station to facilitate the routing of traffic over the tape relay networks.

2. In a message header[?], an address, i.e., group of characters, that specify routing instructions for the transmission of the message to its final destination.

Note: Routing indicators may also include addresses of intermediate points.

Source: from Federal Standard 1037C and from MIL-STD-188 and from the Department of Defense Dictionary of Military and Associated Terms