5
The notification circuits use a 10k end-of-line resistor for supervision. The circuit is monitored
for short and open circuit line faults when in the standby (not energized) condition. In the event of
a short circuit, the NACext will not activate the NAC while the short circuit fault is present.
During coded signal operation, the NACext checks for a short during each “off”, and holds the
circuit off if a short is detected. Short and open circuit faults are reported to the host panel via the
command channel (either SLCnet or hardwired, depending on configuration) and can be identified
by a blinking trouble LED on the NACext during supervisory state.
The NACs are configurable as “Class A” circuits with the addition of an option card that plugs
onto the base board. The option card also provides the additional field wiring terminations needed
for Class A. The NACext monitors for insertion of the Class A Option Card.
In addition, when configured as an SLCnet peripheral, each circuit can be independently
controlled and each has the ability, under software control, to disconnect its supervision, allowing
Earth fault isolation (this operation is also performed automatically as part of the power-up
sequence).
The battery charger charges lead acid batteries up to 18AH. Batteries are supervised for
low/missing battery and depleted battery. The battery charger output remains disabled until a
battery is sensed.
The Canadian version of the NACext includes a low battery cutout module and harness. The
factory installed battery cutout module replaces the standard (US version) battery harness. The
module disconnects the batteries if the terminal voltage drops below 19.3VDC during battery
standby operation. Connection to the batteries is restored on resumption of AC power.
The hardware configuration switch is located at the top edge of the system board (see Figure 1). It
has two functions:
• Switches 1 through 7 identify the optional equipment installed on the NACext. A trouble
condition is reported to the panel if hardware is configured, but not present or hardware is
present but not configured.
• Switch 8 indicates whether the unit is communicating with the Z-28 via SLCnet or over a
hardwired interface.
The Software Address/Configuration Switch (SW2) is an 8-position DIP switch located at the top
edge of the system board. It has two functions:
• When the NACext is operating as an addressable SLCnet peripheral, this switch sets the
SLCnet address to which the NACext responds. Each NACext has a unique address (1
through 250).
• When operating as a NACext non-addressable NAC Extender (conventional or “hardwired”
NACext mode), this switch (SW2) configures the operation of the output NACs, based on the
state of the two NAC control inputs.
Continued on next page
Overview, Continued
NAC (Notification
Appliance Circuit)
Outputs, (continued)
Battery Charger
Battery Cutout
Module (Canadian
Version only)
DIP Switch SW1 --
Hardware
Configuration
DIP Switch SW2 --
SLCnet
Address/Hardwired
Configuration
