When the wheel is revolving at high speed, the wire does not make perfect contact at all points but tends to vibrate and to act as the equivalent of a very high speed interrupter by rapidly opening and closing the circuit.
The basic idea in employing a device and a circuit of this sort in receiving undamped waves is as follows:
When the contact is broken at the ticker wheel and the condenser F C is disconnected from the oscillating circuit formed by the condenser C and the secondary of the receiving transformer, the condenser C accumulates a relatively large amount of energy.
Then when the ticker connects the condenser F C in parallel with C, F C takes the major part of the stored energy and discharges it through the telephones P, causing a click to be heard in the latter.
The interruptions of the "ticker" are very rapid, a great many taking place during the duration of a dot or a dash, so that the resultant clicks occur very close together and the dots and dashes sound very similar to the spark signals of a transmitter sending forth damped waves.
The sensitiveness of the ticker arrangement is very great, in fact much greater than that of any detector.
LESSON THIRTY-FOUR. THE AUDION AMPLIFIER.
The audion amplifier is an arrangement whereby an A audion bulb such as that which has already been described in the Lesson on Detectors is so connected that it acts as a relay and also amplifies minute pulsating electric impulses. An ordinary audion detector bulb will serve as an amplifier bulb but it is usual to modify it somewhat and provide a grid and a wing on both sides of the filament as this arrangement gives the best results.
The audion amplifier is of especial advantage in amplifying weak wireless signals from a detector which would otherwise be unreadable. It is not necessary that the audion amplifier be used in connection with another audion serving as a detector. It will amplify the signals of any other form of detector such as an electrolytic, crystal, magnetic, etc.
