FIG. 78.—Tuning coil of the double slide type.
FIG. 79.—Diagram showing fixed condenser in circuit.
Tuning coils are known as "single slide," "double slide" and "three slide" according to the number of contacts they are fitted with.
FIG. 80.—Fixed condenser.
The loading coil is a supplementary tuning coil used to furnish extra inductance in case it is desirable to obtain a greater range of resonance or tuning.
It is merely a single slide tuning coil connected in series with the regular tuning device. It is not always a necessity but is often part of the equipment when it may be necessary to adjust the apparatus to receive long wave lengths.
Condensers are devices for collecting and storing electricity. They play a very important part in both the transmitting and receiving operations. Condensers and Leyden jars have already been described in connection with the transmitting apparatus.
The condensers used in receiving are very much smaller in size and capacity but are the same in principle. There are two general types of receiving condensers called "fixed" and "variable" accordingly as the capacity is alterable or not.