Address setting means for fire detectors

Details Address setting means for fire detectors Address setting means for fire detectors

1999-03-19

2001-07-03

Crosland, Donnie L. (Department: 2736)

Communications: electrical

Condition responsive indicating system

With particular system function

C340S514000, C340S506000, C340S534000, C340S532000, C340S588000, C340S589000, C340S535000

Reissue Patent

active

RE037255

ABSTRACT:

This invention relates to means for improving the reliability and/or reducing the cost of fire detection systems in which fire detectors are allocated a unique address code corresponding to known locations so that a control unit may selectively communicate with individual detectors at known locations.
In known fire alarm systems there are three methods in common use of setting the address of a detector.
One method is to set the address code in the detector's mounting base. The address may be set actively by altering the position of one or more switches connected to active electronic circuitry in the base, or by uniquely programming an electronic memory connected to such circuitry in the base. This method has the advantage that the address code is not disturbed if the sensor part of the detector which attaches to the base is replaced by another sensor of the same type or of a different type. The control unit will therefore correctly correlate the address code with the location of the detector. A disadvantage of this method is that the electronic circuitry contained in the mounting base may be damaged when high voltages are applied to system wiring for the purpose of checking insulation resistance. A further disadvantage is that in the event of a fault developing in the electronic circuitry contained within a mounting base mounted on a high ceiling, the fault may not be easily rectified without the aid of ladders or scaffolding whereas the sensor may be easily removed with devices generally known as ‘extractor poles’. Special extractor poles can be made for removing electronic assemblies from a base but such assemblies complicate the design of the base, introduce additional mechanical and electrical connections and so reduce reliability and increase costs.
A second method is to set the address in the active sensor part of the detector. This method has the advantage that the active circuitry, i.e. sensor electronics and the communications electronics including the address electronics may be incorporated into one electronics thereby reducing the cost and increasing the reliability of the detector. The mounting base need not contain any electronic components other than wiring terminations and contact means for connecting to the sensor. The base may therefore be subjected to high voltages when the sensor is removed, and, because it contains no electronics the need for access to the base for repairs or maintenance purposes is virtually eliminated. The disadvantage of such a system is that when a sensor is removed from its base for cleaning or maintenance it may in error be replaced by a sensor from another location having a different address to that set in the detector that was removed. In this event the control unit will attribute data from the replaced detector to an erroneous location which may be detrimental to the performance of the system.
A third method is to set addresses sequentially and automatically during system initialisation. With this method the control unit sends an address code to the first detector on the detector wiring circuit. The detector receiving the address stores the address code in its active electronic circuitry and then activates a switch to connect a second detector into the detector wiring circuit. The control unit then sends another address to the second detector and the process is repeated until all detectors have been coded with an address. This technique has the disadvantage that detectors must be wired sequentially or fitted with further electronic means to identify spur wired detectors. Furthermore each detector must contain an electronically controlled switching means which increases cost and may reduce the reliability of the system because the operation of detectors beyond the first detector is dependent on the correct functioning of the first detector.
This invention provides an alternative solution in that the address code is set in the base by passive means only, the sensor having means for reading the address code when it is fitted to the base. After reading the address code, the latter means conditions the sensor to receive signals identified by the address code.
In
a preferred embodiment of
the invention, the address code is set in the mounting base by mechanical means alone and the sensor has means for sensing the position of, or presence or absence of, the mechanical coding means whereby when the sensor is inserted into the base, it is able to read the settings of the mechanical address means and convert them into an equivalent electrical code. Thus the address in the base is transferred to the sensor when the sensor is inserted into the base. In such an arrangement the need for electronic components in the base for address purposes is avoided and detectors can be interchanged without the risk of inadvertently changing the address of the location in which the detector is installed. Thus the invention can be embodied to provide the cost advantages of having all the electronics in the sensor part of the detector with the reliability associated with having the address code set in the detector base.


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IBM Technical Disclosure Bulletin, vol. 26, No. 7, Dec. 1983, p. 3156.*
Interlocutory Decision in Opposition Proceedings Under Article 106(3) EPC, dated Jan. 30, 1998.*
Communication pursuant to Rule 58(5) EPC that Interlocutory Decision is Final, dated May 15, 1998.

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