Motion Picture Herald (Oct-Dec 1955)

nels. one for the auditorium speaker channel, and one spare, which is always in a "warmed-up” condition for ready interchange should one of the six channels in use go bad. In addition, an eighth chassis supplies electronic switching for the auditorium channel. A single high-frequency signal recorded on the auditorium, or "effects,” track and beyond the range of audibility, "triggers" the electronic switcher as required to provide surround reproduction. NO. 2 PANEL This is a two-machine switching-relayequalizer panel, identified by four knobs. This is the "brains” of the control assembly. It provides all of the facilities to allow the projectionist to select operation from Todd-AO, CinemaScope magnetic, Perspecta or regular optical recordings. The panel provides individual equalization and level balancing controls — screwdriveroperated— for twenty magnetic tracks. On a two-projector installation the facilities allow setting the six Todd-AO channels on each projector for identical quality, likewise the four CinemaScope channels on each machine. NO. 3 PANEL This is the master volume control. A five-gang attenuator controls the stage R. L. GROSH & SONS Scenic Studios 4114 SUNSET BLVD. HOLLYWOOD, CALIF. • Curved Tracks Motors Stage Draperies for THEATRE Installations speakers; a single section unit handles the auditorium speakers. The controls are plainly labeled and are of the precision indexed type that provide volume changes in small increments, small enough to prevent annoyance to patrons wThen operated. NO. 4 PANEL I his is the third machine switchingrelay-equalizer panel, providing the same facilities as outlined above for the twTomachine panel. NO. 5 PANEL Monitor selector and volume control panel, providing projectionists with facilities to listen in on any one of the channels, or to check all six channels simultaneously. A separate potentiometer provides means for adjusting the sound level from the booth speaker. NO. 6 PANEL This is an emergency panel. It completes the emergency provision of the amplifier channels. By a simple switching operation, the auditorium power amplifier can be substituted for either of the five stage channel amplifiers. BOTTOM Here is the power supply. A single frame carries — 1. A dual high-voltage and a.c. pow’er supply, providing plate voltage for magnetic preamplifiers, switcher amplifiers, and optical preamplifiers, filament voltage for film preamplifiers, signal lamps and a.c. operated relays. A throw of a switch substitutes the unused section in case of a failure. 2. A dual low-voltage supply utilizing selenium rectifiers and providing d.c. voltage for the magnetic preamplifier tube filaments and for the d.c. relays. The ripple content in this supply is extremely low to provide hum-free operation. Here again the supph is a dual one, a switch providing instantaneous substitution of an unused supply section should the operating one fail. The racks were designed under the direction of E. S. Seeley, now chief engineer of the Altec-Lansing Corporation ; and C. S. Perkins, operating manager of Altec Service; with a major part of the supervisory technical direction performed by Fred Pfeiff, Altec headquarters staff engineer now on leave of absence with ToddAO ; and staff engineer D. Demarest, who supplied the basic drawings from which the rack was conceived and manufactured. The intricate and multiple wiring circuitry w\as installed by Altec electronics technicians M. Toporkoff, N. Troiano and R. Kupchynski, with mechanical engineering details in the hands of T. Carpenter. • New Carbon Coolers for Wide-Screen Projection NEW TYPE Huff "HydroPositive” carbon coolers are used with the “Peerless HvCandescent” lamps installed 'at the Rivoli theatre in New ^ ork for projecting “Oklahoma,” first production in 18 MOTION PICTURE HERALD, OCTOBER 8, 1955