One of the frustrating tasks associated with putting together an RU or RU/GF set is the bewildering numbering system on the connectors. There doesn't appear to be standard Navy five digit numbers mapped to the two and three digit numbers engraved on the connector backshells. This seems to have derived from the original GF and RU set architecture back in 1932, where the connectors were given the number of the entire cable. Thus Cable 37, for example, would have "37" engraved on each of the connector ends, presumably to facilitate final connection.

In an attempt to help sort out these numbers, it occurred to me that an easy method might be to simply have a series of photos, one of each of the junction boxes associated with a given set - since most, if not all, cables pass through the junction box. These junction boxes have had different five digit numbers over the course of time - the earliest I have a record of is CBY-23011 for the GF/RU-2, and CW-62017 for the last RU, RU-19. If you own or have access to one of these junction boxes that is not pictured below (or have a clearer photo than the ones here) please e-mail the photo to