Abstract: A liquid level detector comprising a voltage-divider network, including a thermistor, connected between the terminals of a battery so that the potential at the voltage-divider output varies as a function of the resistance of the thermistor. The voltage-divider output is connected to the input of a voltage-sensitive switching circuit. The voltage-sensitive switching circuit has two stable states and is either in one state or the other depending upon whether the potential at the voltage-divider output is above or below a reference level. When the potential at the voltage-divider output indicates that the thermistor is out of a good heat conductor such as a liquid, the switching circuit closes a series circuit between the battery and an LED provide a visual indication of the low liquid level condition. The thermistor is supplied by means of a constant current source to prevent destruction of the thermistor in the event of a sharp battery voltage increase.