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 measure of value to this reuse project comes from a comparison of how well
the current system serves to counter the vulnerabilities identified in the
threat analysis. The problem of integration arises when various sensors are
grouped into the electronic operating network. The sensor installation and
operation must be examined carefully to determine the relationship of each
device within the system. The advantages of integrating a variety of
sensors are realized in both cost savings and improved protection if system
engineering is done carefully. The engineering task is critical when the
control system and reporting/display terminations are designed. Existing
older control equipment is less likely to fulfill the requirements of an
integrated design due to the lack of expansion capabilities. Although
caution is advised, compatible existing equipment from reputable
manufacturers can be used in updating the control system. Where care is
taken to design-in newer elements consistent with user effectiveness, given
the advent of microprocessor technology and state-of-the-art display,
reduced control systems costs may result in replacement of older networks
with the increased capabilities of the new.
8.4 Reporting and Display System Components. The reporting and display
systems are roughly categorized as follows. These termination options offer
advantages and disadvantages as noted previously. The techniques of
reporting the system detections are indicative of the presentation and
transmission of information. Obviously, the amount of information processed
and displayed increases the cost.
8.4.1 Annunciator Units. Annunciation of alarm signals are presented by
visual and audible indicators which relate to the on/off nature of detection
sensors. Either or both visual and audible indicators are used within a
particular transmission technique that meets the requirements of the
receiving and display system.
8.4.1.1 Modular Single Point Alarm Displays. The technique of alarm
reporting requires that the sensors within a zone are looped to report any
detection on the loop. Typically, this scheme provides visual and audible
indications of alarm conditions. The modular capabilities of this type of
device provide limited expansion in groups of four to 10 sensor zones. The
line security for this type of system is often not present when not in the
armed state. Generally, detection loop length is a short (under 500 feet),
two-wire type on which direct current is also passed. Open or short
circuits are indicative of trouble or alarm. This feature and the "daisy
chain" approach to expansion often defeats the cost-effective benefit by
impeding maintenance of systems.
8.4.1.2 Digital Receiving Devices. Digital receiving devices are used for
centralized reporting of alarm conditions. Individual transmitting devices
report a limited number of signals (less than 10) with a system specific
code number. This system is used in central station and multiple premise
proprietary systems due to the availability of reporting on voice grade
(dial) telephone networks. Upon activation of an alarm device, a
microprocessor circuit initiates a telephone line securing process, dials a
telephone number, identifies itself, and indicates the zone of alarm. The
system of
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