Communications: electrical – Condition responsive indicating system – Specified housing
Reexamination Certificate
2000-02-24
2001-10-02
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specified housing
C340S568100, C340S571000, C340S500000, C340S693110
Reexamination Certificate
active
06297745
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a housing for an alarm, and more particularly relates to a housing for an alarm having a sabotage detector for triggering an alarm signal in the event of cover removal or forcible removal of the alann from the wall.
BACKGROUND
Modem alarm systems are known for high reliability. As a result, such systems, in particular burglar alarm systems, are often subjected to sabotage attempts which range from covering the alarm to ripping the alarm off the wall. Covering or masking of the alarm, which is a method of attacking alarm sensors such as passive infrared alarms, include covering the alarm with a box, hat or other suitable screen or by spraying the entry window of the alarm for the infrared radiation with an infrared-opaque medium. As a countermeasure for this attack mode, an additional detection system is generally incorporated into the detector, such as those which are described, for example, in EP-A-0 186 226, EP-A-0 189 536, EP-A-0 476 397, EP-A-0 499 177 or EP-A-0 772 171 (U.S. Pat. No. 5,942,976).
Another type of sabotage consists of disabling the burglar alarm by unauthorized opening of the cover. A cover contact which is opened upon removal of the cover is often used to detect such sabotage. It is also possible to couple the cover contact to the locking device between base and cover so that operation of the locking device itself is detected (see, in this regard, EP-A-0 616 307).
Yet another form of attack on an alarm system includes physically removing the alarm sensor from the wall on which it is mounted. A system for detecting this type if attached is implemented in at least one known burglar alarm system (type IR160 of Alarmcom AG, CH-8604 Volketswil). This particular detection scheme uses a panel, which is penetrated by a fastening screw of the alarm and is relatively easy to break off the base, and a contact switch. The switch is fixed on a part of the base which is not intended to be broken off and has an actuator portion that presses against a projection of the panel which is intended to be broken off. In the event of the alarm being ripped off the wall, the panel which may be broken off the base remains on the wall and the contact switch is removed from engagement with the panel, thereby opening the electrical contact of the switch. Since the alarm components, particularly passive infrared sensors, are generally intended both for flat wall mounting and for corner mounting, at least two break-off panels must be provided with associated contact switches mounted adjacent to the panels.
Although this known solution has been successful, it requires extra assembly effort and entails additional cost as a result of requiring two contact switches. Accordingly, an improved arrangement for detecting an attack on the mounting of alarm components is required.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present alarm housing is to trigger an alarm signal in the event of forcible removal of the alarm from the wall in a manner which is low cost and easy to install.
A further object of the present alarm housing is to provide an alarm signal in the event of either forcible removal of the alarm from the wall or unauthorized removal of the alarm housing cover.
In accordance with a first embodiment, the alarm housing includes a base and a cover. The base includes a breakaway portion, such as strip-shaped region which is bordered by weak points. The breakaway region has a plurality of screw insertion points for receiving fastening screws there through. A web is included which has a fixed end on the breakaway portion and a free end that projects towards the cover. When the housing is closed, the free end of the web contacts an actuating portion of a contact switch mounted in the cover, thereby activating the switch (e.g., closing the contacts).
In the event that the alarm housing is forcibly removed from the wall, the entire strip-shaped region is broken off the base, removing the web from contact with the switch. As a result, the contact switch for the various types of fastening need be disposed at a single point only. The forward-projecting web and the associated contact switch in the cover achieve the advantage that both opening of the cover and ripping of the alarm off the wall may be detected by a single contact switch. Thus, costs arc reduced by dispensing with one contact switch. In addition, assembly of the alarm is considerably simplified because the contact switch can be pre-installed in the alarm electronics assembly and need no longer be inserted into the alarm on site. This also eliminates any risk of the contact switch being inserted into the alarm incorrectly.
In a preferred embodiment of the housing, the strip-shaped region extends transversely over the base and has screw insertion points for various types of fastening of the alarm, such as wall mounting and corner mounting.
In another preferred embodiment of the housing, the cover includes a printed-circuit board bearing the detection electronics and the contact switch is disposed on the printed-circuit board.
REFERENCES:
patent: 4359646 (1982-11-01), Mejia et al.
patent: 4410884 (1983-10-01), Heiland
patent: 4418336 (1983-11-01), Taylor
patent: 4710629 (1987-12-01), Muller et al.
patent: 4752768 (1988-06-01), Steers et al.
patent: 4880980 (1989-11-01), Muller et al.
patent: 5191314 (1993-03-01), Ackerman et al.
patent: 5194845 (1993-03-01), Sirmon et al.
patent: 5942976 (1999-08-01), Wieser et al.
patent: 0476397 (1992-03-01), None
patent: 0499177 (1992-08-01), None
patent: 0786751 (1997-07-01), None
patent: 0834847 (1998-04-01), None
Catalog Sheet of Alarmcom for “Professional Passive Infrared Detector With Exceptional RF Immunity”, IR160B, Catalog: 1; Section: 2 (1999).
Catalog Sheet of Alarmcom for “Black Mirror”, IR160, (1996).
European Search Report for 99104593 dated Aug. 30, 1999.
BakerBotts LLP
Hofsass Jeffery
Previl Daniel
Siemens Buildings Technologies AG
LandOfFree
Housing for an alarm does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Housing for an alarm, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Housing for an alarm will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2615023