.■IX F.UICTRICAI. FRF.QVr.SCV AXAl.V/.I.K .107 



two I'lul pl.itos in such a way as to form at each imuI of tho ryliiulcr, 

 compariiiu-nts, one sitle of each of which is a diaphragm. Wlicn 

 assoml)li'il the two cliapihragms face each other and are connectedt 

 together by a circular spring made of steel strip. In use the two end 

 compartments are partially evacuated thus causing the diapiiragms 

 to pull apart, straining the spring. When distended the diaphragms 

 lie against the inner faces of the end plates which are shaped as 

 shown. Obviously if air be allowed to enter either of the compart- 

 ments the diaphragm belonging thereto will be pulled toward the 

 other diaphragm by the spring. Passing through the circular spring 

 is a lexer pivoted at one end and carrying on the other end an insulated 

 metallic sleeve. This lever is not attachetl in any way to either 

 diaphragm and will of itself remain in position where last placed. 

 Switch points are mounted in such a way that the sleeve may be 

 forced in or out between them by the action of the diaphragms. 

 This relay has proved very satisfactor\' in scr\ ice and is particularly 

 fast in its operation. 



Connections between the tracker bar, main IkmiIit, .uk! tlu' pneu- 

 matic relays are made by means of rul)ber tubing. As shown in 

 Fig. 3 each of these rehus reciuires two rubber tubes leading to the 

 main header and two from the header to the tracker bar. These 

 tubes are connected to the header by means of stop cocks D so con- 

 nected that the direct passage of air from tracker bar to relay is 

 practically unobstructed liut the passage leading from the junction 

 to the header may be made as small as desired by turning the finger 

 valve. As adjusted, the opening to the header is small compared 

 to the size of the tubes so that if air be permitted to enter one of the 

 tube lines (as at the tracker bar), the diaphragm of the relay a.sso- 

 ciated therewith is immediately released. When the tube is closed 

 again, the entrapped air is soon rcmo\ed through the small opening 

 leading to the header thus restoring the diaphragm to its original 

 position. The relay lever, how'ever, does not follow the diaphragm. 



This arrangement possesses the advantage that small openings 

 only are necessar>- in the player piano roll, and that the opening 

 which connects a condenser into the circuit is not in line on the roll 

 with the opening which tli.sconnects this condenser. Also at the 

 beginning of an analysis by suitable perforations in the roll all air 

 relays can be set simultaneously in the off position (condensers 

 disconnected), thus making sure of the initial conditions. The 

 apparatus is so designed that all the openings causing condenser 

 circuits to close are on one side of the roll and those causing them 

 to open are on the other side. 



