This humidity alarm detector is an automatic humidity detector designed for
civil application, which has 9V battery as the power supply to increase
safetyt. It uses the conductivity of water of the alarm source. It consists
ot gold-plated probe, signal process circuit and Motorolla special IC. When
the humidity reaches a designated threshold value, the metal probe transfers
the detected signal to the internal circuit, which generates the micro-current.

The micro current will generate the alarm signal after it has been amplified.