Abstract: An electronic alarm circuit indicates an abnormal pressure condition in a pneumatic tire on a vehicle. The circuit includes an indicator, either in the form of a light or sound buzzer, or both, which can transmit two distinguishable signals, one indicating the presence of an abnormal pressure condition and the other to test the circuit. An actuation circuit includes a normally open pressure switch which communicates with the internal pressure of the tire and closes upon the detection of the abnormal pressure to activate the indicator. The actuation circuit also includes a resistance connected across the pressure switch to provide a path for electrical current when the switch is open to provide the test signal, as may be desired.