The opposite of astable; it is condition with one stable state. Usually it is used in electronics to describe a particular circuit or part of a circuit. In a monostable circuit, a single pulse is generated by the monostable when it is triggered by a negative input pulse, such as that produced by a push switch connected to an inverted sensor unit subsystem. Once triggered the output remains high for a short period afterwards; that time period is modifiable based on electronic component values. An monostable has one stable state. This type of circuit could be used to give a mechanism a delay. A monostable circuit can be constructed using a 555 timer IC and a few other components. The 555 monostable subsystem provides an output signal that stays high for a period of time before returning to low. It is similar to the delay subsystem but is able to provide a wider range of time delays.