RADIOTELEGRAPHY——-MARCONI. iPAl 
almost completely the spark gap and its consequent resistance, which, 
as is well known, is the principal cause of the damping or decay of 
the waves in the usual transmitting circuit. 
The apparatus shown in figure 6 consists of a metal disk a, having 
copper studs firmly fixed at regular intervals in its periphery and 
placed transversely to its plane. This disk is caused to rotate very 
rapidly between two other disks, 6, by means of a rapidly revolving 
electric motor or steam turbine. These side disks are also made to 
slowly turn round in a plane at right angles to that of the middle 
disk. The connections are as illustrated in the figure. The studs 
are of such length as to just touch the side disks in passing, and 
thereby bridge 
the gap between ie 
the latter. RESONANCE CURVE = 
ye a CurOEN : 
quency employe 
4 PRIMARY CIRCUIT kK 
at Clifden, name- z 
ly, 45,000, when §reAT=-025 ec 
a potential of — torarresistance _ 1405 ws) 
15,000)5, Hy.olésy ois)... PEAUOING SPARE SSe2088 2888 Wave Len 
used on the con- he BARShSR SAS R IN FEET 
denser, the spark KE 
gap is practically 
closed during the 
~ time in which one 
complete oscilla- geri ations CORRESPONDING TO ABOVE RESONANCE CURVE 
tion only is taking 
place, when the 
peripherical alge eas re acre Se ee 
speed of the disk S_- =f Se e~- 
isabout 600 feet  SERIES.or WAVE TRAINS RADIATEL rom CLIFDEN AERIAL 
second. The re- SPARK FREQUENCY SOD FER Sec. 
sult is that the oor 
primary circuit can continue oscillating without material loss by 
resistance in the spark gap. Of course the number of oscillations 
which can take place is governed by the breadth or thickness of the 
side disks, the primary circuit being abruptly opened as soon as the 
studs attached to the middle disk leave the side disks. 
This sudden opening of the primary circuit tends to immediately 
quench any oscillations which may still persist in the condenser 
circuit; and this fact carries with it a further and not inconsiderable 
advantage, for if the coupling of the condenser circuit to the aerial 
is of a suitable value the energy of the primary will have practically 
all passed to the aerial circuit during the period of time in which the 
