Abstract: The positive and negative peak detectors in the interface are reset during each input signal cycle and the reference level used for comparison is switched from one level to another to improve decoding accuracy, with each level determined by the previous two peaks. The input signal is DC coupled and DC offset. The scanner light source is pulsed by a low duty cycle power source if code is not being scanned. The circuit is applicable for digitizing any analog signal with varying amplitudes and/or DC levels and is adaptable to microprocessor control.