The current for the field coil of this unit is supplied by means of a Rectox rectifier unit mounted directly on the baffle. Current for the Rectox is supplied from the 110 volt, 60 cycle, AC source used for the projectors and amplifier. When assembled the unit is similar to the RCA Photophone theatre loud speaker, except that it is smaller.

278. Setting Up the Equipment. -The Photophone portable equipment is in every sense portable. Each individual unit is reasonably small in size, consistent with the requirements of the apparatus, and all shipping cases are within the weight limits for baggage. Due to the simplicity of design the operation of setting up and connecting the apparatus so as to place it in readiness for operation takes but a short time.

The projectors are unpacked and mounted on their stands side by side, with the amplifier on the floor near them as shown in Figure 130. This position is in the rear of the room in which the apparatus is to be used, or in the booth, if one is used. The screen and loud speaker are set up at the other end of the room. Figure 138 shows the relative position of all units, and a cable diagram giving the location and proper position for each cable necessary for the operation of the equipment. The cables are packed with the projectors and amplifier. The accessories trunk (Figure 139), containing necessary tubes, lamps, tools, film magazines for the projectors, etc., should be conveniently located.

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