Abstract: An anti-interference Doppler effect mini-radar includes a generator of pure microwaves, and a receiver for receiving reflected microwaves and coupled to the generator for detecting and demodulating the transmitted and reflected microwave signals. The demodulated signals are applied to a gain controlled preamplifier, and thence to an adjustable gain amplifier. The output of the adjustable gain amplifier is applied to an alarm control circuit. In order to adjust the gain of the preamplifier a servo-circuit is responsive to the input of the alarm control circuit for applying a gain control voltage to the gain control terminal of the preamplifier. A timing circuit responsive to the output of the adjustable gain amplifier blocks the servo-circuit and inhibits the operation of the alarm control circuit for a determined time following the sudden increase in the output of the adjustable gain amplifier.