SECTION
7
MAPNET II@ ADDRESSABLE INTERFACE
INTRODUCTION
Addressable device communications operate via the Simplex Multiple Addressable Peripheral Network (MAPNET
If=). Using a two-wire circuit, individual initiating devices such as automatic smoke detectors, TrueAlarm” smoke
sensors, manual fire alarm boxes, and sprinkler flow switches can communicate their exact identity and status. This
addressability allows the location and condition of each device to be displayed on the interface panel and on the
system annunciators. In addition, notification appliance circuits (horns, bells, strobes, etc.) as well as other control
circuits (fans, dampers, etc.) may be individually controlled. Acombined total of 127 addressable monitor and control
devices may be intermixed on the same pair of wires. If Zone Adaptor Modules (ZAMs) are used, non-addressable
initiating devices can be connected to the MAPNET II@ circuit. The MAPNET II@ option allows the use of addressable
devices and TrueAlarm” sensors with the 4020 system.
TrueAlarm” SYSTEM OPERATION
The MAPNET II@ Controller can communicate with smoke density and temperature sensing devices called
TrueAlarm” Sensors. ATrueAlarm’” sensor measures smoke density, but has no self-contained alarm set point. The
alarm set point is programmed into the 4020. Thus, the alarm decision is made by the 4020, rather than by the
sensor.
Every four seconds, each smoke sensor transmits an output value based on its smoke chamber condition. The 4020
system maintains a current value, peak value, and an average value of each sensor’s output. Status is determined
by comparing the current sensor value to its average value. Tracking this average value as a continuously shifting
reference point filters out the environmental factors that cause shifts in sensitivity. Each sensor’s sensitivity can be
field-programmed at the 4020 panel for different levels of smoke obscuration (in percent). Sensor sensitivity can be
individually varied automatically by time of day, typically more sensitive at night and less sensitive during daytime
hours. In order to evaluate whether the sensitivity should be revised, the peak value that is stored in memory can
be read and compared to the alarm threshold directly in percent.
TrueAlarm’” operation gives the 4020 system the ability to automatically indicate when a sensor is dirty and when it
is excessively dirty. The NFPA 72 requirement for a test of the sensitivity range of the sensors is fulfilled by the 4020
system’s ability to maintain the sensitivity level of each sensor. Additionally, a “two-stage” alarm operation can be
programmed in the 4020 panel. For example, a one-percent smoke obscuration reading could cause a local
indication allowing the building security staff to investigate, while a three-percent obscuration report could
immediately initiate a system alarm.
TrueAlarm” heat sensors provide reading of local temperatures. For fire sensing, rate-of-rise sensing can be
selected as either 15°F or 20°F per minute, with an independent fixed limit of 135’F. For general temperature
sensing, a set point can be selected from 32’F to 158°F and the local temperature readings can be used to warn of
potential problems. The temperature readings can be programmed to read in either Fahrenheit or Celsius.
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