Regency
®
Model 4720 Control/Communicator Installation Manual (P/N 150476, Rev. A) Revised 10/98
11
3.3.2 Fuses
PC board revisions prior to Revision L still use Revisions A-K for overcurrent protection.
• F1 is a 2.5-A Fast Blow Fuse that provides overcurrent protection for an AC Siren Speaker
connected to Terminal 4 of the Model 4720.
• F2 is a 1.5-A Fast Blow Fuse that provides overcurrent protection for touchpads and any
accessories connected to Terminal 5 of the Model 4720.
• F3 is a 1.5-A Fast Blow Fuse that provides overcurrent protection for expansion modules and
smoke detectors connected to Terminal 10 of the Model 4720.
• F4 is a 4-A Fast Blow Fuse that provides overcurrent protection to the battery.
3.4 LEDs
The red LEDs are normally OFF, and come ON under the following conditions:
3.5 Earth Grounding Wire
The magnetic field of a nearby lightning strike can induce damaging currents in the wiring of an alarm
system. Even distant strikes can affect the panel through the AC or telephone wiring. The 4720 has built-in
transient protection devices, but in order to work, they must be able to shunt the transient currents to earth
ground. The green Earth Grounding Wire (included) must have one end installed under one of the four (4)
mounting screws of the Model 4720 printed circuit board. The other end must be connected to a good earth
ground. If this is not available via the ground wire of the building's 3-conductor AC wiring, then a separate
heavy gauge wire should be run to a metal cold water pipe or grounding stake. This wire should be run as
short as possible, and sharp bends should be avoided.
CAUTION:
To avoid fire hazards, the Model 4720 is designed with backup
nonreplaceable fuses in series with the replaceable fuses
(power-limited design). It is
VERY IMPORTANT
that you
replace fuses with
FAST-BLOW
type fuses with the
SAME
AMP
rating as the old fuse. If you replace a fuse with a higher-
rated or slow-blow type fuse, the nonreplaceable fuse will
blow, and the panel will have to be returned to the factory for
repair.
NEVER
put a jumper across any fuse. A jumper across a
replaceable fuse will cause one of the nonreplaceable fuses to
blow. A jumper across a nonreplaceable fuse could cause a
fire.
When a replaceable fuse blows, find the cause of the excess
current by (1) using an ohmmeter and (2) replacing the fuse,
then connecting up one device at a time to see which device
causes the fuse to blow. Repair the short, then replace the
fuse with the same type and rating. Keep spare fuses in your
tool kit.
Table 3.4a: Red LED Indications
LED # Location on PC Board Condition(s) Causing Red LED to Light
1
Top right corner Terminal 4 (AC siren speaker) overcurrent.
2
Lower right side Terminal 5 (touchpads and accessories) over-
current (higher than 1.1 A)
3
Lower right side XBUS overcurrent (higher than 1.1 A).
4
Middle, right side Battery wired backwards.
5
Top, center Terminal 10 (smoke detector) overcurrent.
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