Abstract: The smoke detector includes a light source (1), a measurement section (3) with a measuring receiver (5), a reference section (2) with a reference receiver (4), and an analyzer circuit (6) connected to the receivers. The receivers are of like construction and receive like amounts of radiation from the light source (1). A difference signal (.DELTA.I) formed from the current signal (I.sub.r) of the reference receiver and the current signal (I.sub.m) of the measuring receiver is fed to the analyzer circuit. A reference current (I.sub.k) is superimposed upon the current signal (I.sub.r) of the reference receiver, and the light source is connected to a control circuit and regulated by the control circuit for compensation of the reference current (I.sub.k) by the reference current signal (I.sub.r). The difference signal (.DELTA.I) is superimposed with a compensation signal (I.sub.k ') for zero compensation.