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24 " MOTION PICTURE HANDBOOK the neutral and the left hand bar, which means that they are connected with the opposite side. Thus far, if the circuits are all working and have equal number of the same candle power lamps the board is equally "balanced." The next, or top circuit, however, wc find to be connected to the neutral and the right hand bar so that there are three contacts with six circuits on one side and two contacts with four circuits on the other. COUNTING THE SCREW HEADS IN EITHER OUTSIDE BAR WILL TELL YOU THE NUMBER OF CONTACTS THERE ARE ON THAT SIDE. One side of ALL circuits are connected to the neutral (center) bar. To lind which side a circuit is connected to, disregard the screw heads in the center bar and find the screw connecting it to the outer bar. This will show you which side it is on. These two illustrations are given that you may study them closely. Large switchboards are very confusing, but as a matter of fact they are extremely simple. Remember that the light circuit running from a three-wire board HAS BUT TWO WIRES, NOT THREE. Remember, also, that a circuit can be, and usually is, run each way from a switchboard con- tact; in other words, each contact usually carries two separate and distinct circuits. Pulling switch c kills the whole board, of course, and ex- tinguishes every light it controls. Blowing a fuse on the two-wire board has the same effect, except that the wires will still be alive in the sense that a shock will be had if you touch them. Fuse-blowing on the three-wire board is more complicated, however. If one of the outer fuses blows the lights on the circuits connected to that side will go out, but those on the other will still burn. If the central (neutral) fuse blows out there will be no effect at all provided the board is evenly balanced—has an equal number of candle power on each side. This is by reason of the fact that under these conditions there is no current in the neutral wire at all, the lamps of the two sides burning in series with each other. If, however, there be a greater candle power on one side than on the other there is curent flowing in the neutral wire equal to the difference and if the neutral fuse blows the side having the lesser candle power will burn above candle power until the fuse is reinstalled. This is the practical effect of the blowing of a neutral fuse since the even balanc-