Moving Picture World (Jan-Jun 1909)

668 THE MOVING PICTURE WORLD b-b the fuses, c the main house switch and d-d-d-d-d-d-d-d-d-d the circuit service switches. The two rows of circles are the circuit fuses, being of the "plug" variety, (B, Fig. 10). Looking closely you will see screw heads in the face of the bars. These screws indicate the contacts, circuits being run in either direction from each contact. As to the two-wire board, I do not believe any explanation is necessary; but the threewire board is more confusing, though it is quite simple after all. I have numbered the circuit contacts of this board (B, Fig. 8) i-i, 2-2, 3-3, 4-4, 5-5. Now an examination shows us that circuits 1-1 have contacts with the right hand and neutral bars, as have also circuits 2-2, which means that these four circuits (there arc two circuits to each contact, if all arc working) are on one "side." Circuits 3-3 and 4-4, however, we find to have contact with 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." Circuits 5-5, however, we find to he 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 WILT. TELL YOU THE NUMBER OF CONTACTS THERE ARE ON THAT SIDE. One side of ALL circuits are connected to the neutral (center) bar. To find 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 contact; in other wrords, each contact usually carries two separate and distinct circuits. Pulling switch c kills the whole board, of course, and extinguishes every light it controls. Blowing a fuse on the two-wire hoard 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 he a greater candle power on one side than on the other there is curcnt flowing in the neutral wire equal to the difference and if the neutral fuse blows the side having the greater candle power-will burn dim until the fuse is reinstalled. This is the practical effect of the blowing of a neutral fuse since the even balancing of a three-wire system is seldom accomplished, though it might be balanced evenly enough on one board to show no perccptihlc effect through the blowing of a neutral fuse. The reasons for the installation of three-wire systems will be explained under "Wire Systems" further on. The main house switchboard should invariably be mounted mi slate, marble or other insulating, non-combustible material and the whole hoard should be enclosed in a metal cabinet with a door having a substantial, easily manipulated latch. If the board is of considerable size it should be placed in charge 0 fsome competent man and none other lie allowed ueh it. The fuses of all circuits, except the stage, exit and operating room arc lamp circuits should be located on the main switchboard. The proper place for the main house switchboard is the lobby, preferably at a point from whence a view of the stage, or curtain, may he had. The writer considers it exceedingly d practice to have the main switchboard equipped with two main switches, as follows: The main house switch which everything except the exit lamps and a sub-main switch which, pulls all lights it is desired to extinguish to darken the auditorium, with the exception of one circuit handled by the operator a afterward explained. Darkening the auditorium by pulling half a dozen circuits 01 another makes a very had effect. This switch should not prevent the installation of all the regular circuit switches but be supplemental to them. This applies to large houses only, where then itorium circuits. On large switchboards it is well to label all switches plainly, indicating just what circuit they control, thus: "Proscenium," "Ceiling Clusters." etc., etc. EXTRA LIGHT CIRCUITS. In some cities it is required that extra lights be operated with non-explosive oil burned in suitable lamps. If electric light is allowed for exit lamps the circuit should in all cases be controlled from the box office, never from the main switchboard, and this circuit should in no case be controlled by the main house switch. There is no telling what a blanked fool will do when excited. He might pull the main house switch at an alarm of fire, thus throwing everything, including the exit lights, in darkness. Tap in your exit light circuit ahe'ad of the main house switch (i. e., between the switch and the street mains) and run it directly to a switch located in the box office, where proper fuses should be installed. Thence run the service wires to the various exit lamps. Exit lamps should be enclosed in a box with ground glass front on which the word "EXIT" has been blocked out in translucent red, the letters not less than five inches in height. These signs should be placed over all exits and the lights in them be kept burning at all times when an audience occupies the auditorium. It is desirable that one of the auditorium circuits, preferably the ceiling lights, be controlled from the operating room, as well as from the main switchboard. This is accomplished by running the circuit service wires from the main switchboard service switch through the operating room, bringing them past a position on the wall DIRECTLY IN FRONT OF THE OPERATOR and in easy reach from operating position. Install a sub-service switch so that the operator can reach both it and the dowser at the same time. Now when the signal is given the operator to start, all the circuits except that controlled by him are pulled from the main switchboard. The operator, when ready to start, pulls the above described switch with one hand as he pulls the dowser or starts the machine with the other. The effect is to darken the house and throw the picture at one and the same instant. In stopping the order is reversed and the picture is off and the lights on simultaneously. It is NOT advisable to have all circuits handled thus, since the man at the main switchboard should be able to light the auditorium instantly, in case of alarm, which he could not do were all circuits controlled by an operating room switch, until the operator threw in his switch. The main switchboard service switch of the circuit controlled by the operator is not touched at all — is left shut at all times except when the house is closed. Fig. 9 Fig. 10