Abstract: A voltage meter includes a sampler, a gain circuit, an accumulator and a feedback circuit. The sampler samples an input signal to generate a series of first signals and a series of second signals. The gain circuit, coupled to the sampler, modifies at least one of the series of first signals and the series of second signals, to generate a series of modified first signals and a series of modified second signals. The accumulator, coupled to the gain circuit, accumulates an operational result of the series of modified first signals and the series of modified second signals, to generate an accumulation result. The feedback circuit, coupled between the accumulator and the sampler, sends a feedback signal back to the sampler according to the accumulation result.

Abstract: The present disclosure illustrates a code activation device used to transmit an activation signal to a back-end device, so as to activate the back-end device. The code activation device comprises a sensing module and a processing module. The sensing module comprises a sensor unit, and the sensor unit generates sensing signals according to a preset action of a trigger object. The processing module connected to the sensing module receives the sensing signals, generates a sensing beat according to interval periods between the sensing signals, and determines whether the sensing beat matches a preset beat, wherein the processing module generates the activation signal when the sensing beat matches the preset beat.