Motion Picture Herald (Jul-Sep 1931)

September 26, 1931 Motion Picture Herald IS trol equipment under (/) and (;) is mounted on inclined side panels. {K) Telephone to ten stations mounted on left vertical panel. (jL) Terminal and plug boards. On the keyboard section of the console are located the 36 individual controls spaced 15 sixteenths of an inch on centers. Each control has the following associated apparatus starting with the lower key row and going up. First, a two-position tilting tab switch that transfers the control from the hand operated individual potentiometer to the associated foot-pedal-operated subgroup master potentiometer. Second, an individual control drum for direct control of lamp intensity, which is set at zero scale for black-out, and at 10 for fullbright. Third, a pilot lamp to indicate when the control is energized. Fourth, a strip of interlocking keys that connect the control to anyone of the six control buses ; namely, individual, grand-master, and the four group-masters. Fifth, a two-position tilting tap switch for selecting either preset of manual. Sixth, a group of fourscene present potentiometers that are set at zero scale for blackout, and at 10 for full-bright. Seventh, a cross connecting selector button for connecting or disconnecting the predetermined loads and the control circuit. Eighth, a cross connecting pilot lamp button. And ninth, a twoposition tilting tab switch for throwing the control "on" or "off." ON A FOUR-INCH-WIDE panel running from top to bottom through the center of the keyboard, is mounted all master controls. At the top is a clock, while just below is the preset indicator. The scene flasher keys and pilot lamps follow. Below these are the motor switch and rheostat, while on the same section the grand master and preset fader magnetic clutch switches are located. The reduced speed clutch switch is next with the four group master interlocks from handwheel to motor control and the four master selector switches just below. On the bottom section are the "black-out" and "master" kevs. Voltmeters are located on either side of the cue sheet holder just above the keyboard. These voltmeters give the operator continuous indication of the main d. c. generator voltage and of the grand-master generator voltage. On the vertical panel, immediately in front of the operator, are six slow-motion handwheels for master control, and one wheel for the scene fader assembly. To obtain a clear understanding of how the switchboard is set up, we will go through the sequence of operation from starting the motor generator set to shut A rectifying tube nvitit the cover removed. The unit is located in the basement. ting it down. First, we will assume for the time being that the predetermined load circuits have been connected to the appropriate controls. By closing the "master" switch on the console, the line feeding the motor of the motor generator set is closed, and at the same time contactors on the reactor rack, which supply 115 volts 60 cycles to the tube units, close in. After a time delay of sufficient length to allow the filaments to become heated, a second set of contactors close in, energizing the anodes or main circuits of the tubes. When the motor generator set comes up to speed, the voltages of the generators are set at their proper values by rheostats on the motor generator set panel. Power is now supplied to the tube units and to the console as far as the black-out contactor. By closing the black-out switch, the main generator and the grand master generator leads are now connected to their associated control buses. Now let us assume that control No. 1 is to be operated individually. Since the negative side of all potentiometers are tied together, we are only concerned from what bus or source the positive side is fed. Working from the lower row of the keyboard up, the tilting tab transfer switch remains in its normal position, since it is not desired to control by sub-group master. The next row containing the individual potentiometer may be set for any intensity desired when the lights come on. Just above is the strip of interlocking keys, and the key marked "IND" should be closed, which connects the positive side of the individual and preset potentiometers to direct feed. The tilting tab selector switch will now be closed to the "manual" position, which connects the moving arm of the in{Continued on page 64)