A. B. ColeSales Manager ― De Forest Radio Tel, & Tel. Co.

“ The process of testing Audion Bulbs is one of the most careful and expensive tests in the entire electrical industry. A bulb used in the proper detector may give extremely loud signals from stations twenty or thirty miles away, and yet not be really sensitive to weak signals from great distances, or it may give much weaker response to nearby stations than a crystal detector and still be extremely sensitive to weak signals over long distances. ”

“ There are many operators of experience with the Audion who know of all the above points, and many more who do not, and these suggestions, the result of long and active experience of one who has corrected more Audion troubles than perhaps any other one individual, should be given that close attention and careful consideration which they deserve, that the very best of results may be obtained and the longest possible ranges covered. ”

“ So much has been written without authority of the patentees which is partially incorrect or serves to cause the experimenter to aspire to fields which cannot he achieved in a practical fashion by him and so many false directions have been given for making apparatus from the regular Audion Detector for which it is not adapted, that it seems only right to set the experimenter on the proper track, showing what can be done and how to do it, pointing out the fallacies in statements made by unauthorized parties. ”

“ It is remarkable how easy it is to have trouble if the circuits and parts of the detector as a whole are not correct, and this is one of the main reasons why the bulbs are not furnished separately and why all guarantees are immediately dissolved if an Audion bulb is used otherwise than in the Audion Detector made for it. ”

“ Regular Audion Detector Bulbs are not adapted for the reception of continuous waves, because the vacuum is not correct for the purpose and because the filaments must be operated at such a high intensity that they give very short service, making them unnecessarily expensive. ”

“ If a small box is made, large enough to hold one 3 cell flashlight battery, and a switch is mounted on the box, and arranged to cut in one cell at time, and this device is connected in series with the telephone receivers, and the receiver binding posts on the detector, a very satisfactory adjustment will be provided, enabling the operator to accomplish excellent results with bulbs otherwise considered less sensitive than standard. ”

“ The Audion is selective to some extent as to spark frequency, but positively is not selective as to wave length. It is exactly as sensitive at 3000 meters as at 200. If you will consider the proportions of an amateur tuner, you will realize that it is most efficient from 200 to 1500 meters. ”