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MANAGERS AND PROJECTIONISTS 1037
well remember the struggle I had trying to dope out the electrical action from drawings and "explanations" made by engineers when I was trying to get some sort of understanding of electrical mysteries. The engineers meant well, but failed to understand how puzzling some things might be to the novice, but seem as clear to them as the country air.
This far we have examined the principle of vacuum tube rectification only, and that principle would not have much value as an amplifier "B" battery eliminator, for the following reasons :
(a) A battery is necessary to heat its filament.
(b) The rectified current is of the same voltage as the supply, which usually is 110, and in amplifier operation higher voltages usually are necessary or desirable.
(c) We only "get" half of each wave, hence the current comes in jerks, with gaps between each half wave. It would be what is called a strongly pulsating current. Not only that, but also only half the power is available.
We therefore must go further, and Fig. 390 illustrates, in diagrammatic form, the way those drawbacks may be avoided. At the left side of the diagram are leads connecting to the 110-volt A. C. supply. This current does not go direct to the rectifier tubes, but to the two transformers, Tl and T2 (transformers are used to change the voltage of A. C. power; as shown in the diagrams they have two windings, the primary winding, connected to the supply leads, and the secondary, connected to the circuit using the power). Tl delivers a low voltage for lighting the filaments of the vacuum tubes VI and