International Review of Educational Cinematography (Jan-Dec 1932)

154 R. C.A. portable Photophone. This projector, as all R. C. A. products, is highly developed and very peactical. It is the result of more than a year of research and trial. The whole outfit comprises a projector, an amplifier, a loud speaker and film magazine. Its total weight is just over 200 pounds. The dimensions of the projector are 19" X 19" X 10" and those of the amplifier (in a portable case with lid) 26" xS3/i/" X 11", the loud speaker, a flat diffuser model is contained in a case 8 %" X 19" x 1.4%". The projector takes standard film and gives a clear image 24 X 3 m at a distance of 22 m. The sound is sufficient for an air space of 15,000 cubic feet with an 8" speaker and one of 12,000 cubic feet with a 6 inch speaker. The projector may be operated from alternating current mains of 105 to 125 volts, 50 or 60 cycles monophase. Total consumption at 100 volts is 12 amps. Contact with mains is through a fourway cable and plug : one for feeding the projector, one for the amplifier, one for the synchronising circuit between projector and amplifier and one for that between the latter and the loud speaker. The outfit is complete with fire proof 1,000 foot spool bones, lenses with focal lengths varying between 90 and 20 mm, a 1000 watt 110 volt projection lamp, a 10 volt 7.5 amp. exciting lamp and a photoelectric cell type U X 868. SMALL FRENCH SOUND EQUIPMENT The French industry has likewise put on the market sound equipment for small halls and portable equipment suitable for teaching, propaganda tours, popular education, etc. Amongst the most interesting projectors is the Jacky Stellor, by Debrie, sound star type D, by Etoile Film, Nalpas, type E, Royal Amplitone type Z, by Benwood. The first, the Jacky Stellor, an extremely simple projector, is particularly suitable for small portable work ; the two others are semi-portable projectors suitable for slightly larger work. The Royal amplitone, however is also made in a portable model. The Jacky Stellor is an excellent adaptation of the Jacky silent projector, whose qualities of stability, strength and reliability have gained it great popularity in France and abroad. The Stellor has great advantages in transport, for the sound equipment is completely independent of the projector. It is contained in a metal box and is composed of soundhead, photo-electric cell, pre-amplifier and amplifier. The box measures 55 X 35 X 15 cm. and is placed during projection on the tripod and under the projector. The sound equipment in its box is mounted entirely on felt and rubber in order to give perfect protection against projector vibrations. The valves are also mounted in non-vibrating holders. Great care has been taken to insure regularity of film speed through the sound head. Special devices insure a constant speed even in the case of line voltage changes with their resultant change in motor speed. The excitor lamp works at 6 to 8 volts. The photo-electric cell has a calcium element and is equipped with a mask which eliminates all parasitical noises. The amplifier has 3 stages : one stage of pre-amplification, one stage of intermediate (which, with the pick up becomes a voltage amplifier), and one power stage. A modulated output of 4 watts is assured. The electro-dynamic loud speaker is perfectly adjusted to the power stage and the reproduction is good. Amongst other advantages the Jacky