A monitoring system for monitoring an escalator is provided including: a local gateway device; and a sensing apparatus in wireless communication with the local gateway device through a short-range wireless protocol, the sensing apparatus including: a frequency detection device configured to detect frequency data of the escalator, wherein the sensing apparatus is configured to obtain a specific frequency of a component of the escalator and detect at least one of a change in the specific frequency of the component to a sub-frequency, a direction shift of the specific frequency of the component, and a change in a harmonics of the specific frequency of the component in response to the frequency data.