Some details of this device and the trials undertaken by the RFC (No. 2 Squadron initially and also fitted to HMA Gamma)on two sizes of the ‘James Mean’ device can be found in AIR 1/811/204/4/1249, with correspondence going on until early 1914. It was rejected, apparently not that distinct. It also appears that it could not be used with ‘Gnomes’ so presumably no rotary engine.
‘The Aeroplane’ by Claude Grahame-White and Harry Harper also mentions the device on page 159.
(On the 26 September 2014 at the London Branch of CCI I gave a talk on ‘Solving Communication Problems in the RFC’, it included some information on the ‘James Mean’ device.)