Abstract: A duct heater control module for controlling an electric duct heater in an air duct. The duct heater control module includes a microcontroller for receiving an air flow signal from an air flow sensor for controlling the electric duct heater in response thereto. The microcontroller controls short cycling of the current switching relays, determines the nature of the input signal from a thermostat, and drives a status display.

Abstract: A drawing take off system itemizes components shown on a paper drawing. The take off system includes a sleeve for holding a standard pen, a computer having a software module, and an interface connection between the sleeve and the computer. The software module maintains a list of each component model shown on the drawing. The sleeve includes a pen stroke switch for counting pen strokes and a component selection switch for selecting a component model from the component model list compiled in the software module. As an estimator marks components on the paper drawing, the take off system counts pen strokes for each individual component of each model of component marked on the paper project drawing by the estimator and calculates the cost for all of the components taken off of the paper drawing.