Black Box LPH240A-H, Operation Manual

Page: 48 / 56

Chapter 4: Operation
724-746-5500 | blackbox.com Page 48
4.4 Hardware operated Alarm Contact for monitoring internal
power supply
The two screws Alarm Contact features are standard on
LPH240A Series, and provide Normally Closed (NC) contacts to which
the user can attach one sets of status monitoring wires at the green
terminal block. When this option is present, the terminal block for Alarm
Contacts is part of the Power Input panel in the LPH240A case. The DC
power input connection is in the same panel.
The NC Alarm Contact is held close when there is power on
the main board inside of the LPH240A. This provides a “Hardware
operated Alarm” because the NC contacts will open when internal power
is lost, either from an external power down condition or by the failure of
the power supply inside of the LPH240A Switch.
Useful info about Alarm Contacts in LPH240A:
1.
Two-position terminal block (1,2) provided next to the DC
power input, as shown above.
2. The Alarm Relay contact connected to the two terminals (1,2) is
hardware operated.
3. By default it is NC (normally closed). It will open if there is any
loss of power to the electronics inside of the unit.