Intrusion alarm system with automatic exit control and misset indicator

Claim 1

An intrusion alarm system comprising: a mode selection circuit which selects a "Present" mode which represents the presence of a resident in a house, building, room or the like and an "Absent" mode which represents the absence of the resident from the house, building, room or the like, said mode selection circuit being set by the resident; a door open/closed detection circuit which detects a door's being in an open state or a closed state; a sequential circuit which operates while said mode selection circuit is set in the "Absent" mode and stores signals representative of the door being opened and then closed according to said door open/closed detection circuit, said sequential circuit detecting that the door was opened for a second time after the mode selection circuit is set in the "absent" mode, and producing an output signal upon the detection of the second door opening; a misset alarm device which generates an alarm if an opening of the door is not detected by said door open/closed detection circuit within a predetermined time after said mode selection circuit is placed in the "Absent" mode; a timer circuit which starts counting upon said second door opening detected by said sequential circuit and produces an output signal upon expiration of a predetermined time as counted from the second door opening; and an automatic information device which informs a security center of the detection of a trespasser when the output signal of the sequential circuit and the output signal of the timer circuit are both present.