saturated in a period of high conduction of led 18 the indicator is either a bright or blinking light and the intensity is determined by the led 18 characteristics the saturated terminal voltage at 42 and the value of resistor 36 the duration of the period is governed by the time constant of the r c circuit including capacitor 24 and feedback resistor 32 once capacitor 24 is discharged and the voltage on terminal 38 drops below that of terminal 40 led 18 ceases to conduct capacitor 24 is then charged up again through resistor 20 and the led 18 will once again start to conduct if the microwave signal after amplification brings the output voltage at 42 above the diode threshold with for instance the resistors 20 and 32 having values of 1 megohm each and the capacitor 24 having a capacitance of 0 2 microfarad the rate of blinking light is about 1 3 second when the signal input is removed either by turning the microwave source off or by removing the device from the field of radiation the led 18 stops conducting the circuit conditions return to normal and amplifier 30 returns to linear gain operation when the device is turned on by the push button switch 28 and current starts to flow in the biasing networks for the detector.