Usually, a sensor that how defends a system (include urgent button) for a defence area, defence area type but below reduce 3 kinds:
1.Cannot defence area of withdraw a garrison (24 hours of defence area) : Any moment spark effective. The aerosol sensor that is like urgent pushbutton, fire control and harmful gas sensor.
2.But withdraw a garrison not delay time defence area (instantly defence area) : After domestic member comes home but withdraw a garrison, the place troops on garrison duty when leaving home; Once spark instantly effective. Wait like sensor of burglarproof infrared ray, window magnetism sensor.
3.But defence area of delay time of withdraw a garrison (delay time defence area) : After domestic member comes home but withdraw a garrison, the place troops on garrison duty when leaving home; The delay time after should sparking period of time ability is effective, inside this paragraph of time but withdraw a garrison. Be like sensor of burglarproof door magnetism.

How to prevent a system to want to detect circumstance of each defence area, prevent a person how to defend a system to destroy. Accordingly, defence area has 3 kinds of state:
1.Value having block (if 10K is ohmic) : Normal circumstance. Port is received or string together in the output of sensor namely receive a resistor to come true.
2.Short circuit: Spark call the police. Be opposite in defence area port after sensor movement ground short circuit.
3.Open circuit: Be called the police by clipping. When clipping sensor port and defence area port connect a line, defence area port forms open a way.