I wrote: > It appears that by the time the RAV and RAX-1 appeared in 1940, the USN > had dropped any requirement for 12-vdc liaison receiver sets. I ignored the 1941 RU-18 liaison receiver set. I guess there must have been some call for a 12-vdc installation somewhere as late as 1941. They must have used a GO-9 or a GP-7 with it. Mike / KK5F