Battery Cables; Dc Power Switch; Overcurrent Protection; Polyswitch® Circuit Protectors - Regency 4720 Installation Manual

Regency ® Model 4720 Control/Communicator Installation Manual (P/N 150476, Rev. A)

Battery Cables

3.1
The red (+) and black (–) battery cables are used to connect a 12-V
not provided) to the system. The battery provides backup power to the Model 4720 in the event of AC
power interruptions (failures).
Observe proper polarity when connecting the battery cables of
the Model 4720.
Note: The Model 6712 12V, 6.5-AH battery will provide at least four (4) hours of standby operation to the basic
4720 system. Two (2) 6.5-AH batteries are required for household and commercial fire installations. The
use of accessories may reduce standby operation time so that additional battery capacity may be needed.
Note: If the AC transformer is unplugged for more than 24 hours, the battery must be disconnected to prevent it
from being discharged.
Figure 3.1a:

DC Power Switch

3.2
The DC power switch is used to remove DC power from the circuitry of the Model 4720. When this switch
is in the OFF position with AC connected, the only thing that remains functional is the battery charging
circuit. If AC is not connected, the standby battery should not be connected, because leakage current
through the charging circuit could discharge the battery over a period of time. See Section 3.12.3 for
information on enabling and disabling the DC power switch.

Overcurrent Protection

3.3
PolySwitch ® Circuit Protectors
3.3.1
Starting with the Revision L printed circuit board, all fuses have been replaced with PolySwitch
(copyright Raychem) circuit protectors. The PolySwitch's normally very small resistance (less than
1 ohm) undergoes a large, abrupt increase when it gets heated by an overcurrent condition. When the
current returns to an allowable value, the PolySwitch resets automatically, allowing normal circuit
operations to resume. The protector requires no manual resetting or replacement. If a red LED is on,
determine where the problem is (refer to Table 3.4a) and correct it. The LED will turn off.
CAUTION:
Battery Connection—PC Boards Prior to Revision L
10
Revised 10/98
rechargeable battery (Model 6712—
DC