Battery Charger; Power Failure/Emergency Transfer Unit (Dpft) - Toshiba Strata DK24 Installation And Maintenance Manual

INSTALLATION-SYSTEM DESCRIPTION
SECTION 400-096-202
SEPTEMBER 1992
Quantities of PCBs
Installed (Including PCTU)
Estimated Operation
Time (Hours)
Approximate (-24V) Current
Drain (DC Amperes)
Time is estimated with the following considerations:
(1) Batteries have full charge at start of operation.
(2) Batteries (2 ea.) are connected in series.
(3) Batteries are 12 VDC, rated at 80 amp/hours each.
(4) System is operating at full load traffic with LCD-type telephones.
(5) Batteries used for this test are gel-cell, maintenance-free batteries. Reserve duration will vary
depending on battery type and manufacturer. These figures should only be used as an estimate.
4.12 A Toshiba-supplied, 9-foot battery cable, part
number PBTC, supports the reserve battery instal-
lation.
IMPORTANT NOTES!
1. Local ordinances may dictate battery
type and installation details.
2. The reserve power batteries must be
installed while commercial AC power
is applied to the system to allow the
power supply reserve relay to operate.
If batteries are connected after AC
power is lost, the batteries WILL NOT
power the system and the system WILL
NOT operate.

4.20 Battery Charger

4.21 To allow full normal system operation during
a power failure, the power supply has a built-in,
current limiting battery charger that maintains cus-
tomer-supplied batteries. Electrical characteris-
tics of the battery charger include:
•
Nominal float voltage: 2.275 volts/cell
•
Charge current: 0.7 amps maximum
Battery discharge cut-off voltage: 20.5 ±0.5V
•
TABLE 2-A
TYPICAL RESERVE POWER FUNCTION ESTIMATES
2 3 4 5
71 45 31 23
1 1.7 2.4 3.1
2-6
6 7 8 9 10
19 16 13.5 11.5 10
3.8 4.5 5.2 6 6.6
5 POWER FAILURE/EMERGENCY
TRANSFER UNIT (DPFT)
5.00 The DPFT provides an optional means of
ensuring uninterrupted telephone operation in the
event of a power failure. The DPFT (Figure 2-8)
automatically connects selected CO lines to stan-
dard telephone lines in the event of a power failure,
while permitting normal operation when the sys-
tem is in service.
5.01 The DPFT is a self-contained module that
mounts externally to the key service unit (KSU),
typically near the main distribution frame (MDF).
Connections to the CO lines, standard telephones,
and the KSU are made with two 50-pin amphenol-
type connectors on the DPFT.
5.02 The DPFT consists of eight normally open
relays, connecting the telephones to PSTU (Stan-
dard Telephone Interface Unit) printed circuit board
PCB circuits and the CO lines to PCOU (CO Line
Unit) PCB circuits (Figure 2-9). If a power failure
occurs, the relays close, connecting the telephones
directly to the CO lines. Calls can then be placed
from the selected standard telephones over the
CO lines, completely bypassing the system.
11 12 13 14 15
9 8 7 6 5
7.3 8 8.7 9.4 10