C. Power Supply Circuit Board Assembly.
The power supply printed circuit board contains circuitry that provides DC operating voltage
to units in a SelecTone system and maintain a charge level on the batteries when AC power is
available. It also includes logic circuitry that controls the AC power LED, DC power LED and
transfer of battery connection to the output during an AC power outage.
II. SPECIFICATIONS.
Determining the maximum load discharge current from a specific battery size over a specific
amount of time can be tricky. Batteries are rated at maximum efficiency over a 20 hour discharge
period. Therefore, a 20 amp-hour battery will provide 1 amp over a 20 hour period. However,
calculating discharge time for other discharge currents is not as easy as division or multiplication.
A 20 amp-hour battery will supply 1 amp for 20 hours. However, it will not provide 2 amps for 10
hours, but rather, 1.8 amps for 10 hours, which is equivalent to 18 amp-hours.
EXAMPLE:
Your system has a 12 amp-hour battery and you need 4 hours of backup time. Simply locate the
12 amp-hour diagonal line and the 4 hour horizontal discharge time line. Next, find the intersec-
tion (as circled). Follow this intersection point vertically down to find the maximum discharge
current. In this case, 2 amps is the maximum discharge current.
Operating Voltage
120 VAC, 50/60 Hz
240 VAC, 50/60 Hz
Current Requirement
120VAC, 0.90 amps
240 VAC, 0.45 amps
DC Output (Power-Limited, Supervised)
AC Power Applied
Voltage
24.8 VDC no load
23.8 VDC full load
Current
2.5 Ampere maximum
Ripple
0.5Vrms maximum
During Power Failure
Voltage
26.4 VDC no load
24 VDC nominal
Current
2.5 Amp maximum
(25° C - see Note 1)
Output Circuits (Power-Limited)
2.5 Amp @ 24VDC Resistive
Dry Contact Closure
of Trouble Out Relay
Connect to power limited circuits only
AC fail relay
1 amp 120 VAC/28 VDC
Battery trouble relay
5 amps 120 VAC/28 VDC
Battery Package
Number of Batteries
2, connected in series
Battery Voltage
12V each (24V total)
Capacity
7 Ampere-hours
Type
Sealed, lead-acid gelled electrolyte
Recharge Time
48 hours (after complete discharge)
Charging Current
1.25 Amps maximum
Physical
Dimensions (HWD)
15.50” x 12.50” x 4.50”
Weight
11 Pounds (without batteries)
Operating temperature Range
0° C to +49° C
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