The strongest emission in the helium‐neon gas maser corresponds to transitions between the 2s2and 2p4states of neon which have angular momenta of 1 and 2, respectively. These levels split up in a magnetic field and the maser output contains differently polarized radiations of slightly different frequencies. In particular, for a small magnetic field parallel to the maser axis two circularly polarized components of different frequency are emitted. Their superposition may be described as linearly polarized light where the plane of polarization is rotating at half the difference frequency. A polarizer in the beam gives rise to amplitude modulated light. Interesting effects may be observed when the various Zeeman components resonate in different cavity modes of the Fabry‐Perot interferometer.