We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
560 RICHARDSON'S BLUEBOOK OF PROJECTION
matter which exciter is lit at the moment, or how the switches happen to be set, throwing either switch over will turn out the lamp of the projector then operating, and simultaneously light the other, thus effecting changeover of sound at the end of each reel.
Figure 139 illustrates many of the fundamental principles of amplifier circuits that were discussed in the preceding parts of this section on Amplifier Theory and Wiring, and at the same time shows how designing engineers vary and combine the application of those principles. The use of coil L-4 in Figure 139 represents one such variation. Condensers C-7 and C-2 represent another. The reader must always expect to find some novelty in any amplifier diagram he may have occasion to trace. Some will be found in Figure 140.
The Circuits of Figure 140
In this widely used amplifier two noteworthy features are found in the switching arrangements and binding posts of the lower left-hand corner. In this area of the drawing fuses F-l and F-2 mark the terminals through which 110-volt line power is supplied to the amplifier. Tracing this pair of wires straight right, through the switches D-l and D-2, we see that they terminate at the primary windings of two power transformers, T-4 and T-5. A glance at the secondaries of these transformers shows that T-5 is the high-voltage instrument providing plate power, since its secondary is wired to the plates of vacuum tubes V-5 and V-6. However, these tubes seem to have grids grounded to their plates, a peculiarity of interest, worth returning to consider. Meanwhile, we note that T-4 has two secondaries. The right-hand one lights the filaments of the two tubes V-5 and V-6, while the left-hand secondary lights the filaments of tubes V-3 and V-4, which apparently are wired in a push-pull stage. Whether or not this is really the case is a question that can be deferred until the speech circuits of those tubes are traced. It is a prime mistake, in analyzing the wiring drawing of an amplifier, to try to see too much at one time. At present we are tracing