Any plans around for those machines? I found elements for WWII in patents but so far nothing on the Paraboloïde Baillaud or other exotic devices (télésitemètre Perrin for example). Those would make intriguing models ...
This may not be what you are looking for, but I have a photo of Perrin télésitemètre, that I have attached along with a few other rare ones. A German Hornbostel apparatus, and early British design (Sorry I don't no the correct name) and an American Exponential Horn. I find these contraptions equally interesting, good look in finding any patents or drawings.
Thank you . so far I only found a Perrin patent but it describes only one "hearing" module, not the complete device. I have some Sautter-Harlé patents from the thirties wich could be combined to give a nearly complete view of the machine but no dimensionnal data. This is a subject that has not been properly researched so far (at least not from a modelling point of view)
It just happen that I went through some files about Belgian sound detectors. As they were mounted on automotive trailers, they qualify for my study about Belgian military vehicles up to 1940. After an European survey and purchasing one BBT, the Belgians did purchase a number of Skoda/Teppaz system in the late thirthies. Useds with some successes in 1940.
Around 1930, they looked at the systems of Bar & Stroud, Barbier, Bénard and Turenne, Goerz, Harlas and Brazda, even professore Ronchi's idea, but strangely enough no German at that time !?
More names ! thank you... Ok I got some patents from the guys you quoted, although not much is useable for modelling work. Harlas seems especially to be the pure scientific/theoretical guy rather than the type who patents complete artefacts.
but what do you mean about Giorgio Ronchi's "idea" ???
And did you find anything like blueprints for my prime interest : the Baillaud Paraboloid and the Perrin télésitemètre?
) and an American Exponential Horn. 
