International photographer (Jan-Dec 1934)

August, 1934 The INTERNATIONAL PHOTOGRAPHER Tiventy-five MOTION PICTURE SOUND RECORDING (Continued from Page 19) horns were also turned on and their switches set on tap twenty, they would not disturb the impedance match. For three horns, possihle combinations would be taps two, six and eight ; or taps four, six and six. The exact combination used in any particular case depends on the comparative volumes of sound required of the several horns. Photo-Electric Cell Monitoring The two relays that are shown in the diagrams are known as relays No. 1 and No. 2. Their windings are energized by current from the twelve-volt storage battery that supplies power to the signal system. Two key switches mounted on the mixer panel in the monitor room control the relays. Another set of key switches installed in the middle amplifier bay permits the transmission engineer to operate the relays when making gain runs or other tests on the recording system. When relay No. 1 is in its normal position, the circuit is connected for direct monitoring. When relay No. 2 is normal, its blades are connected to the photo-electric cell amplifier in film recording machine No. 1. If the monitor man closes the key switch controlling relay No. 1, that relay is energized and connects the monitoring amplifier to the photo-electric cell monitoring circuit. Since the No. 2 relay is normal to PEC amplifier No. 1, the monitoring amplifier is connected in the above case to that PEC amplifier. But if the key switch associated with relay No. 2 is also closed, the energizing of that relay transfers the monitoring amplifier to the output of PEC amplifier No. 2. This arrangement provides the monitor man with means for checking at any time on the continuity of the film recording circuits. No means is available for him to check on the wax (or disc) recording machines; but that is not necessary because the recording engineer keeps the cutting of the wax record under constant observation during recording to determine if there is any cutting over between grooves. The photo-electric cell amplifiers will be described in the chapters on film recording, which will be the subject that will be begun in next month's issue. ftu0 j Ampro U^REGULAfc$l50°=° GUARANTEE "I personally guarantee money back. I guarantee the 400 watt Biplane Filament Mazda equal to '■en watt in illumi. Best 16MM Value Bass . . . value Under . . . offers Precision Made Ampro . . .New guarantied — at a saving of S50.50 — Powerful — Brilliant — Plastic projection — Long-life— Smoothness — Quietness assured. 400 wait Biplane Mazda light is equal to 500 watt. Kodacolor may be used. Instrument complete with cord and plug — instructions — tarrying case. fully guaranteed for one year. Regular $150 00; Bass price $99.50. full details and Ban Bargaingram No. 212 ii free on request. DEALERS: WRITE FOR DETAILS BASS CAMERA CO. 179 W.Madison St. Chicago DR. G. FLOYD JACKMAN. Dentist Member Local No. 659 706 Houn Hollywood : 9 to 5 First INat'l Bldg., Hollywood Blvd. CLadstone 7507 And by at Highland Appointment MOVING PICTURE MONTHLY All About The CINEMA WORLD IN INDIA Annual Subscription — Inland — Rs. 3-8-0 Outside of India— 7 Shillings or $2.50 Send to Motion Picture Monthly, Khatav Bldg., Ciegaum, Bombay, 4, India The Roto-Tank showing Film and Separator 16 and 35 mm. Positions of Rotor The New HOLLYWOOD ROTO-TANK Specially designed for users of Contax, Leica, Military Cameras, 16 mm. and location tests on sound and action recording units. A maximum of agitation is produced in this unit, insuring shorter developing time with color separations and gradations unobtainable by other methods. No pre-soaking, no air bells, no streaks. The entire unit is constructed of heavy bakelite of low conductivity. 25 feet of 35 mm. or 50 feet of 16 mm. Price— Postpaid in United States $25.00 For details regarding the Roto-Tank and larger units write ROY DAVIDCE FILM LABORATORIES, Ltd. 6701 Santa Monica Blvd. Hollywood, California Please mention The International Photographer when corresponding with advertisers.