[Illustration: Fig. 769.--Organ blower speed regulator; diagram showing operation and method of installing. A cord running from the top of the organ bellows passes over two pulleys and is then made fast to the chain furnished with the regulator. This chain passes around a sheave which turns on a post projecting from the center of the slate panel. Attached to the lower end of the chain is a weight, also furnished with the regulator. As the air is exhausted from the bellows the latter slowly collapses, drawing the rope down with it, and in so doing turns the sheave from left to right, thus cutting resistance out of circuit and increasing the speed of the motor which pumps air into the bellows. Responding to the inrush of air, the bellows expands, relaxing the tension on the rope which is now pulled in the opposite direction by the weight, thus turning the sheave from right to left, cutting resistance into circuit once more and slowing down the motor. The speed of the motor is thus automatically regulated by the bellows, with the result that a practically uniform pressure is maintained at all times. In connection with an organ blower regulator it is necessary to install a separate starting rheostat. This is required for the reason that all organ bellows leak. During the intermissions in the musical part of the service, or at other times when the blower is not operating, the air gradually escapes and the bellows settles down, moving the rheostat arm to the right and cutting out resistance. With the motor at rest and the bellows empty all the blower regulator resistance would be short circuited and it is therefore necessary to avoid throwing the motor directly across the line when starting again. A starting rheostat with no voltage release is suitable for this purpose, and should be installed within easy reach of the organist, so that a moment or two before beginning to play he can move the lever of the starting box and get the motor into operation. Where remote control is desirable a self starter can be substituted for the manually operated starting box, in which case the entire installation can be controlled by a push button, or single throw knife switch.]