HEBTZIAN WAVE WIRELESS TELEGRAPHY. 153 



a dot or a dash, according to the disposition of the holes on the first 

 strip. Accordingly, taken as a whole, the receiving arrangement is not 

 capable of being influenced so as to print a telegraphic sign except by 

 the operation of a series of wave trains succeeding one another at cer- 

 tain assigned intervals of time. 



An improvement has been latel}^ described by the same inventor* 

 in which the apparatus used, although more complicated, performs the 

 same functions. At each station two instruments have to be employed; 

 at the transmitting station one to effect the conversion of Morse signals 

 into the properly arranged series of wave trains, and at the receiving 

 station an instrument to effect the reconversion of the series of wave 

 trains into the Morse signals. These are called respectively the dis- 

 ])enser and the collector. The details of the arrangements are some- 

 what complicated and can only be described by the aid of numerous 

 detailed drawings, but the inventor states that he has been able to 

 carry on Hertzian wave telegraphy by means of these arrangements 

 for short distances. Moreover, the method lends itself to an arrange- 

 ment of multiplex telegraphy, by sending out from different trans- 

 mitters signals which are based upon different arrangements of time 

 intervals between the electric wave trains. Although this method 

 may succeed in preventing a receiving arrangement from being in- 

 fluenced by vagrant waves or waves not intended for it, yet an objec- 

 tion which arises is that there is nothing to prevent any one from 

 intercepting these wave trains, and with a little skill interpreting their 

 meaning. Thus, if the record were received in the ordinary way on 

 a simple receiver, corresponding to a Morse dot would be printed five 

 dots at unequal intervals, and corresponding to a Morse dash would 

 be printed two such sets of five dots. A little skill would then enable 

 an operator to interpret these arbitrary signals. On the other hand, 

 the inventor asserts that he can overcome this difficulty by making 

 intervals of time between the impulses in the series so long that the 

 latter become longer than the intervals between each of the series of 

 waves which are dispatched in continuous succession when the key is 

 pressed for a dash. In this case, when telegraphing, the series of dots 

 would overlap and intermingle with each other in a way which would 

 make the record unintelligible if received in the usual manner, but 

 would be perfectly legible if received and interpreted by a receiver 

 adapted for the purpose. 



Another way of obliterating the record, as far as outsiders are con- 

 cerned, is to interpolate between the groups of signals an irregular 

 series of dots, i. e., of wave trains, which would affect an ordinary 

 coherer, and so make an unintelligible record on an ordinary receiver, 

 * See Electrician, Vol. I., p. 418, January 2, 1903. 



