Show variable to take up little room no two sets seta operate on the same me value 0 of resistance resistance when using tho the re distance coupled type of audio fre quency amplification the resists resistance nee should be adapted to the characteristics of the tubes used the aging of tile the tubes and tile the changing voltage of the U B battery variable resistance may be made so BO as to occupy very little room nearly oil all commercially made variable are so made that it la Is awkward to mount them tho the diagram indicates at a room saving method use a n base of hard rubber or bakelite 2 by ia 1 by 3 MO 16 inches which Is slit in two places about three fourths fourtha of the length of the block the resistance element Is made by dipping a strip of cardboard in waterproof india ink the are usually arranged in pairs one of the making making contact with ROLLER a r leads eliminated and efficiency of set Is increased tile the plate and B plus pill supply the other making a connection from the grid of the amplifying tube to the filament sliders are made from sheet brass and electrically connected to the contacts at one end of the resistance by a soll sol tiered dered flexible wire be sure that the flexible wires are well insulated roller holler conflicts contacts on the india ink resistance insero that the ink will not be scraped off or injured these rollers are made by mounting about four of the ordinary spacing wn washers from commercial variable condensers on n one eighth inch briss bar lie he certain that the pressure of the rollers on oil the resistance strip Is firm and secure the figure shows how this unit may be placed between two tube sockets in such a manner as aa to conserve space and save wiring all but one lead to the n B plus supply long binding post bolts tire are substituted for the short ones onea usually found in commercial tube sockets and the variable resistance unit and the fixed condenser tire are bound to tile the socket terminals with the same game bolts news |