An apparatus for calibrating and testing a pressure switch, the apparatus comprising: a) a housing including an inside and an external surface; b) an air compressor located on the inside of the housing, the air compressor having a vacuum-side inlet and a pressure-side outlet; c) a first vacuum inlet nozzle in fluid communication with the vacuum-side inlet of the air compressor, the first vacuum inlet nozzle being located on the external surface of the housing; and d) a positive pressure outlet nozzle in fluid communication with the pressure-side outlet of the air compressor; e) a circuit board located on the inside of the housing; f) a battery located on the inside of the housing for supplying power to the circuit board; i) a pair of conductivity indicator lead inputs (176, 178) located on the external surface of the housing and in electrical communication with the circuit board; j) a conductivity indicator light located on the external surface of the housing and in electrical communication with the circuit board, wherein the conductivity indicator light is operable to visually indicate whether the pressure switch is open or closed; and k) an on/off button located on the external surface of the housing for completing an electrical circuit between the battery and the circuit board, wherein when the on/off button is placed in the "on" position, the circuit is completed and the battery, the air compressor, and the conductivity indicator light are operational; the apparatus being characterized by further comprising: g) an increase voltage button located on the external surface of the housing and in electrical communication with the circuit board, wherein activating the increase voltage button will cause the circuit board to increase the voltage supplied to the compressor pump; h) a decrease voltage button located on the external surface of the housing and in electrical communication with the circuit board, wherein activating the decrease voltage button will cause the circuit board to decrease the voltage supplied to the compressor pump; when the on/off button is placed in the "on" position, the increase and decrease voltage buttons, are operational. a) a housing including an inside and an external surface; b) an air compressor located on the inside of the housing, the air compressor having a vacuum-side inlet and a pressure-side outlet; c) a first vacuum inlet nozzle in fluid communication with the vacuum-side inlet of the air compressor, the first vacuum inlet nozzle being located on the external surface of the housing; and d) a positive pressure outlet nozzle in fluid communication with the pressure-side outlet of the air compressor; e) a circuit board located on the inside of the housing; f) a battery located on the inside of the housing for supplying power to the circuit board; i) a pair of conductivity indicator lead inputs (176, 178) located on the external surface of the housing and in electrical communication with the circuit board; j) a conductivity indicator light located on the external surface of the housing and in electrical communication with the circuit board, wherein the conductivity indicator light is operable to visually indicate whether the pressure switch is open or closed; and k) an on/off button located on the external surface of the housing for completing an electrical circuit between the battery and the circuit board, wherein when the on/off button is placed in the "on" position, the circuit is completed and the battery, the air compressor, and the conductivity indicator light are operational;