【正文】 all sensitive areas of the plant or the building. Most fire codes state the requirement for monitoring and control specifically related to a type of a plant or building such as chemical plants, petroleum, nuclear plants, residential highrises etc. A general conclusion of these codes can be specified as the following requirements :(a) The source of all detector signals should be exactly identifiable by the central station(b) An extra path of munication between the central station and all local controllers(c) Direct means of control of alarm and central equipment by the central station(d) Means of munication between the central station and the fire department(e) Availability of emergency power supply. The codes usually also specify the types and frequency of tests for all equipment.A fire detection and alarm system is a bination of devices designed to signal an alarm in case of a fire. The system may also acplish fan control, fire door hold or release, elevator recall, emergency lighting control and other emergency functions. These additional functions supplement the basic system which consists of detection and alarm devices and central control unit. Technology has an influence on system architecture. When technology changes, the architecture has to be revised to take advantage of these changes. In recent years, VLSI technology has been advancing at an exponential rate. First NMOS and, in the last year or two, CMOS chips have been produced with the same packing density with more gates per chip yet at a lower power consumption than NMOS. Surely this change in technology must affect our design of hardware at both the chip and the system level. At the chip level, single chips are now being produced which are equivalent to board levels of only the previous year or two. These chips have microprocessor, memory in RAM and ROM, IO Ports both serial and parallel, A/D timer, flags and other functions on chip. At the system level, the new chips make new architectures possible. The objective of this paper is to show how technology can influence system architecture in the field of fire control. The new high density single chip microcontrollers are incorporated in the design of a large scale system and yet we obtain a smaller system with a better performance. In terms of fire detection and alarm monitoring, this is reflected directly in the local station hardware, because of their remoteness and power supply requirements. A plete local station can be designed around a single CMOS chip with power consumption of a few m W depending on system operation. This approach reduces the cost and plexity of design, implementation and maintenance and provides easily expandable and portable design. This implementation was not possible with old technology. Most of fire detection/monitoring systems available are tailored towards a specific application and lack the use of recent advances in CMOS VLSI technology. In this study, we develop a fire detection/monitoring system which is general in concept, readily implementable in a multitude of applications for early detection of a fire before it bees critical, for equipment and evacuation of personnel. Here, we propose a central control and distributed control/detection/monitoring with adequate munication, where use is made of singlechip microcontrollers in the local stations, thus improving controllability and observability of the monitoring process.2 Detection and alarm devicesA basic fire detection system consists of two parts, detection and annunciation. An automatic detection device, such as a heat, smoke or flame detector, ultraviolet or infrared detectors or flame flicker, is based on detecting the byproduct of a bustion. Smoke detectors, of both ionization and optical types, are the most monly used detector devices. When a typical detector of this type enters the alarm state its current consumption increases from the pA to the mA range (say, from a mere 15pA in the dormant mode to 60 mA) in the active mode. Inmany detectors the detector output voltage is well defined under various operating conditions, such as thosegiven in Table 1:Table 1 Typical detector voltage output levelsvoltage levelDetector condition22VDetector is in open circuit condition13V~22Vdetector is normal1V~13Vdetector is in an alarm state1Vdetector is in short circuit conditionThe more sensitive the detector, the more susceptible it is to false alarms. In order to control the detector precisely, either of the following methods is used: a coincidence technique can be built into the detector, or a filtering technique such that a logic circuit bees active only if x alarms are detected within a time period T. The detection technique depends greatly on the location and plant being protected。 this satisfied all our memory and 1/0 requirements at the local station side.4 System implementationThe local station: Fig. 3 is the block diagram of the circuit used to utilize the MC68HCllA4 as a remote fire detecting circuit while Fig. 4 illustrates the same circuit in an expanded form. It can be seen that the single microcontroller can be used to monitor more than one detector, thus reducing system cost. Closed loop connectionsThe loop power supply, which is usually between 28 and 26 V, is further regulated by a 5 V 100 mA monolithic low power voltage regulator to supply power to the microcontroller. The onboard oscillator, coupled with an external crystal of MHz, supplies the microcontroller with its timing signal which is divided internally by four to yield a processor frequency of kHz, which is an even multiple of the RS 232 [7] baud rate generator. In this Section the term ‘supervised input or output’ will be used to mean that the function in question is monitored for open and shortcircuit conditions in addition to its other normal functions. More information can be found in Reference 9.5 Main loop Main loop flow chart6 Conclusion