| 摘要 |
A controller for operating devices adapted for motor control, such as dampers, valves and the like in a heating, ventilating and air conditioning (HVAC) system interfaces with a serial link which may carry control signals for operating a multiplicity of controllers on a time division multiple access (TDMA) basis has digital circuitry responsive to the control signals which translates them into digital signals which are stored between access times. Two series connected pluralities of resistors define, between their opposite ends and their junction points, a potentiometer which is variable by normally open and normally closed contacts which individually are connected across each resistor in each of the pluralities. The switches are operated in response to the digital signals so as to vary the resistance presented by the potentiometer between the opposite ends thereof and the junction. The potentiometer is connected as two arms in a bridge motor control circuit so as to enable the integration thereof into computer controlled HVAC systems which receive and transmit inputs and outputs along a link or bus interconnecting the computer with a multiplicity of controllers.
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