International photographer (Jan-Dec 1935)

April, 19S5 The INTERNATIONAL PHOTOGRAPH H K / wenty-seven strip and panel should be of the standard nineteen-inch length so that they may be mounted in a relay rack with the sound amplifiers. The two transformers used are the standard type of impedance-matching transformer that is widely employed provide losses when operated between such circuits of ten and twenty decibels, respectively. The following five jacks are connected to another impedance-matching transformer that has four windings. When both the primary and secondary double windings S-QO SOO™ /2S' LJII^} Primary ' secondaries iodb zodb soo" soo" soo~: £oow 500" :6+w soo" :i6" > 6< > o © O ( > » . '3o" /JO*" j 4 | til ffo 1 fl tlwii i £ a i+i 0 ? Q <? =3NiZ PAD PRIMARIES ^SECONDARIES Fig. 5. Suggested arrangement of the test panel. in sound recording installations. The first transformer has three windings and is connected so that by patching into the first and second jacks a 500-ohm to 500-ohm impedance match may be obtained. This arrangement is used when it is desired to join two circuits of 500-ohms impedance without creating a direct-current path between them. When the first and third jacks are used, the same transformer provides a 500-ohm to 125-ohm impedance ratio by paralleling the secondary windings. A special jack is required for this purpose, as may be seen. This 125-ohm output may be coupled into a 200-ohm circuit with but little reflection loss (since we know that it is not particularly harmful to feed from a lower to a slightly higher impedance) ; and it is frequently used for this purpose. The next four jacks furnish access to two attenuation networks of the //-type which are intended for operation between circuits of 500-ohms impedance, and that are in series, this transformer has an impedance ratio of 500 ohms to sixteen ohms. When the two primaries are in series and the two secondaries in parallel, the impedance transformation is from 500 ohms to four ohms ; and when the primaries are in parallel and the secondaries in series, the impedance ratio is 500 ohms to sixty-four ohms. These thorough descriptions of the jack arrangement employed in sound studios and of the construction of the test panel were presented both with the hope that they would be of use to soundmen and budding soundmen and that they might be of practical help in the design of small sound recording or public address systems, or aid in the arranging of an experimental laboratory. This method of installing apparatus and bringing out terminations in jack strips should be of particular interest to radio store owners and experimenters, as it contributes to the neatness with which equipment can be arranged in a shop. FLASHES FROM THE COLOR-FRONT (Continued from Page X) laboratories and studios all over the world, scientists and cameramen are striving to perfect color-cinematography. The one who succeeds will be he who simplifies a foolproof system that does not add too much to the cost of production or complicate the process of projection. Some contend this is a sort of "irresistible force meeting an immovable body" proposition. But cinematographic experts and experimenters recognize "no such animal." They are like the chap in Edgar Guest's poem who, when they said it couldn't be done, proceeded to do it. There is no last word in any department of human endeavor. As fast as a problem is solved, another one develops out of the solution. That's what really gives zest to life and keeps up the people's interest in it. If for no other reason, color must eventually be brought to the screen ; for the picture audience of today demands life "as is." Proof of this is to be seen in the "hand" accorded a good color short-subject, even in the most lowly of picture palaces. This naturally infers a color cvcle that will take many moons to run its course. OLD TIMERS (Continued from Page 12) I have seen the old-timer take the part and do it without rehearsal. Some day a producer or a director with an eye for business will quietly round up all these men and women and sign them up on long term contracts as extras. No, he won't be a philanthropist. He will be a smart busi ness man who will realize that the talent scattered among the old-timers will save him money and help him make better pictures through their ripened experience of years before the camera. The background will be worthy of the best he can put in the foreground. Please mention The International Photographer when corresponding with advertisers.