Control Panel Type 9

One of the well-known members of this forum currently has listed on ebay a Control Panel Type 9, Section Ref 5U/2548.

Does anybody have any information regarding what it was used with, neither he nor I know.

A.P.2463 says the Type 9 is ‘For control of rotary convertors’, but with no further detail, and that it’s covered by A.P.1186D Section 1 Chapter 4 (A.L.50). Unfortunately the copy I have as a pdf has chapter 4 ‘To be issued later’, so no help at all!

Any information would be very interesting.

Many thanks,

Andy