Bosch D125B - Manual

Fire Alarm Systems | D125B Dual Class B Initiating Module

D125B Dual Class B Initiating Module

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Two separate powered detector loops

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Suitable for 12 VDC or 24 VDC, two‑wire or
four‑wire detectors

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Up to 50 two‑wire 12 VDC glass break detectors

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Reports individual loop alarm, individual loop
trouble, and ground fault

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Manually resets latching devices from control panel
or remote central station

The D125B has two separate NFPA Class B (Style B)
powered loops. The module supervises each of the
loops for opens, shorts, or ground faults. Both loops
can be powered with either 12 VDC or 24 VDC to
connect compatible two-wire detectors or other two-
or four-wire devices such as retarded waterflow
switches, manual stations, heat detectors, or glass
break detectors.
The D125B is suitable for connecting fire or burglary
devices in commercial, industrial, and institutional
applications. Schools, offices, and health care facilities
are typical commercial applications.

Functions

Loop Supervision

The D125B needs to be electrically connected to earth
ground and to the control panel's common. The D125B
has a supervisory output terminal for each of its loops.
All terminal designations are clearly marked on the
module circuit board.
To supervise the loops, install an end-of-line (EOL)
resistor beyond the last detector of each protective
loop. If you are replacing a D125 or D125A Module
with the D125B, use the 1.5 kΩ resistor
(P/N: 15-03130-000) installed with the original system.
If

you are installing a D125B in a new system or are

adding additional devices to an existing system, use
the 1.8 kΩ resistor (P/N: F01U009011) supplied with
the module.
The D125B shorts the protective loop on the control
panel when the high (+) and low (-) side of either
module loop is shorted together or when a smoke
detector activates. The D125B opens the protective
loop on the control panel during the following
conditions:

• Either of the module protective loops are opened.
• The D125B Interface module is unpowered.
• Either the high (+) side of the loop or the low (-) side

of the loop is shorted to ground.

With the D9412GV3, D7412GV3, D7212GV3,
D9412GV2, D7412GV2, D7212GV2, D9412G, D7412G,
and D7212G Control Panels, a short to ground causes
a ground fault condition when ground fault detect is
enabled.
When programming for fire applications, refer to the
appropriate control panel's operation and installation
guide.

Notice
Do not mix 12 VDC and 24 VDC detectors on the
same D125B Module.