An interface for processing a variable reluctance sensor signal provided by a variable reluctance sensor, comprising: a detect comparator (108, 302) for comparing the variable reluctance sensor signal with a reference signal, the detect comparator (108, 302) being configured to: (i) assert a zero detect signal, when the variable reluctance sensor signal reaches the reference signal; and (ii) de-assert the zero detect signal, when the variable reluctance sensor signal falls below the reference signal; an integrator (106, 305) including an input for receiving the variable reluctance sensor signal, and including an output providing an integrated signal which is indicative of total flux change of the variable reluctance sensor; an arming comparator (110, 306) which compares said integrated signal with a predetermined arming threshold, and which provides an armed signal when the integrated signal crosses the predetermined arming threshold; wherein the reference signal and the predetermined arming threshold are selected so that the armed signal is provided at a time after the zero detect signal is asserted; and a detect circuit (112, 310), the detect circuit (112, 310) being configured: (i) to assert a cross detect signal when the armed signal is provided; (ii) then to de-assert the cross detect signal when the zero detect signal is de-asserted; and (iii) to provide the cross detect signal as a reset signal to the integrator (106, 305), the integrator (106, 305) being configured to use the cross detect signal to keep the integrator (106, 305) reset while the cross detect signal remains asserted, and then to clear the integrated signal. a detect comparator (108, 302) for comparing the variable reluctance sensor signal with a reference signal, the detect comparator (108, 302) being configured to: (i) assert a zero detect signal, when the variable reluctance sensor signal reaches the reference signal; and (ii) de-assert the zero detect signal, when the variable reluctance sensor signal falls below the reference signal; (i) assert a zero detect signal, when the variable reluctance sensor signal reaches the reference signal; and (ii) de-assert the zero detect signal, when the variable reluctance sensor signal falls below the reference signal; an integrator (106, 305) including an input for receiving the variable reluctance sensor signal, and including an output providing an integrated signal which is indicative of total flux change of the variable reluctance sensor; an arming comparator (110, 306) which compares said integrated signal with a predetermined arming threshold, and which provides an armed signal when the integrated signal crosses the predetermined arming threshold; wherein the reference signal and the predetermined arming threshold are selected so that the armed signal is provided at a time after the zero detect signal is asserted; and a detect circuit (112, 310), the detect circuit (112, 310) being configured: (i) to assert a cross detect signal when the armed signal is provided; (ii) then to de-assert the cross detect signal when the zero detect signal is de-asserted; and (iii) to provide the cross detect signal as a reset signal to the integrator (106, 305), (i) to assert a cross detect signal when the armed signal is provided; (ii) then to de-assert the cross detect signal when the zero detect signal is de-asserted; and (iii) to provide the cross detect signal as a reset signal to the integrator (106, 305), the integrator (106, 305) being configured to use the cross detect signal to keep the integrator (106, 305) reset while the cross detect signal remains asserted, and then to clear the integrated signal.