A single push-button on Model 303 causes the digital display in automatic rotation to show its three functions of: voltage, outside air temperature (Fahrenheit), outside air temperature (Centigrade). When the radio master switch of the aircraft is first turned on, The Model 303 always readsout the aircraft voltage to the nearest tenth of a volt. A code letter E indicates it is in the voltage function (EMF). To display outside air temperature in degrees Fahrenheit, the button is pressed, and the letter F appears to indicate this mode. The next press of the button displays C for outside temperature in degrees Centigrade.