An encoder comprising a magnet, AMR or GMR sensors arranged to generate two analogue signals and means for evaluating the said two analogue signal (60, 70) created by the sensors; Characterised In That: the encoder is a rotary encoder; the means for evaluating comprising two means (90, 100) for digitising the said two analogue signals (60,70) generated by the sensors, one of the two means (90, 100) arranged to provide a lower resolution digital representation of the said two analogue signals (60, 70) than the other means; the encoder arranged to be switched to a power saving state for a predetermined period of time, to be at least partially re-activated after the predetermined period of time and to compare a current value derived from the analogue signals (60, 70) with a stored previous value derived from the analogue signals (60, 70); wherein a magnetic field generated by the magnet is not monitored in the power saving state; wherein the encoder is arranged to, when partially activated, create a current digital representation (110, 120) of the said two analogue signals (60, 70) using the lower resolution digitisation means, to compare the current digital representation (110, 120) of the analogue signals (60, 70) with a stored previous digital representation of the said two analogue signals (60, 70), to reactivate further if the comparisons indicates that the current and previous digital representations differ and to create, using the higher resolution digitisation means when further activated, a digital representation of the said two analogue signals (60, 70) having a higher resolution than the digital representation (110, 120) of the analogue signals (60, 70) created when partially activated. the encoder is a rotary encoder; the means for evaluating comprising two means (90, 100) for digitising the said two analogue signals (60,70) generated by the sensors, one of the two means (90, 100) arranged to provide a lower resolution digital representation of the said two analogue signals (60, 70) than the other means; the encoder arranged to be switched to a power saving state for a predetermined period of time, to be at least partially re-activated after the predetermined period of time and to compare a current value derived from the analogue signals (60, 70) with a stored previous value derived from the analogue signals (60, 70); wherein a magnetic field generated by the magnet is not monitored in the power saving state; wherein the encoder is arranged to, when partially activated, create a current digital representation (110, 120) of the said two analogue signals (60, 70) using the lower resolution digitisation means, to compare the current digital representation (110, 120) of the analogue signals (60, 70) with a stored previous digital representation of the said two analogue signals (60, 70), to reactivate further if the comparisons indicates that the current and previous digital representations differ and to create, using the higher resolution digitisation means when further activated, a digital representation of the said two analogue signals (60, 70) having a higher resolution than the digital representation (110, 120) of the analogue signals (60, 70) created when partially activated.