Abstract: The present invention relates to a fuse loss indicating system for monitoring the condition of a plurality of fuses in an electric circuit. The indicating system includes a plurality of individual indicator circuits, one for each fuse to be monitored. Each indicator circuit includes an optical isolator for electrically isolating the indicator circuit from the monitored circuit. When a monitored fuse blows, the associated optical isolator triggers a flip flop to generate a fuse loss signal to cause a warning LED to light and alert an operator as to which fuse has blown. In its preferred embodiment, the fuse loss indicating system is utilized to monitor the fuses in an SCR motor bridge circuit. In this embodiment, the fuse loss system also generates a bridge disable signal when a fuse blows to cause a bridge lockout circuit to disable the gating signals to the SCR's, thereby disconnecting power from the motor.

Abstract: This invention is directed to a variable air volume cooling system for a building which utilized changes in the diameter of the belt going around a two piece driver pulley and a follower two piece driven pulley to effect changes in fan speed and, accordingly, the air volume supplied. A control means to operate a servo-motor connected to the driver pulley provides for separating the two piece driven pulley to slow the fan, driving the two pieces of the driven pulley together to speed up the fan, and for maintaining the same speed should a desired temperature range be obtained. The control compares the temperature of the area to be cooled with the speed of the fan to produce its outputs. Deadband operation is provided to eliminate toggling and other excesses of output reversals.