The interference which results from the first of those two sources is readily overcome since the oscillator of a wireless receiving station may always be given a metallic connection to the earth sufficient to maintain it clear of statistical charges without in any appreciable degree interfering with its operation as a receiving oscillator.

Thus, for instance, if the vertical oscillator includes a condenser insulating a portion of the vertical oscillator from the earth, the condenser may he shunted by a coil of inductance so large that for the high frequencies employed in wireless telegraphy it shall operate practically as an open circuit, while affording a ready path to earth for the electrical charges which would accumulate upon the vertical oscillator and produce disruptive discharges to earth.

Again, if a highly sensitive detector or receiving device be included directly in the vertical receiving oscillator, such an inductance coil may he placed in shunt to the receiver without appreciably affecting its apparent sensitiveness. The coil will then serve as a by-path for the currents due to the passage of the charges of the vertical oscillator to the earth.

Another device which may serve to still further protect the receiver under these conditions is that illustrated in Fig. 1, in which V and V are portions of the vertical oscillator system, L is a coil of large inductance, R is the receiving device, and C is a condenser of capacity so large as not to impede appreciably the passage of the high-frequency oscillations of wireless telegraphy while acting practically as an open circuit for the more slowly varying currents by which the vertical oscillator is maintained free of static charges.

The greatest security from this form of interference is, however, obtained by providing the vertical receiving oscillator with an adequate conductive connection to earth and by placing the receiving device in a local circuit made resonant by a coil and a condenser to the frequency of the electrical oscillations to which the receiver is intended to respond.

Fig. 1.

An example of such an arrangement is shown in Fig. 2, in which VI2 is the vertical receiving oscillator 11 12 are the two coils of a high-frequency transformer, R is the receiver, C2 is a condenser and L2 is an inductance coil.

The manner in which the local circuit containing the receiver is made resonant to the frequency of the oscillations which it is intended to respond will be considered later in this paper. It is sufficiently high that the local circuit being resonant for the purposes of wireless teleg-graphy will not be appreciably affected by the more slowly varying currents in the vertical oscillator by which the latter is maintained free from static charges.