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CHAPTER 3: INSTALLATION ELECTRICAL INSTALLATION
MULTILINK ML1600 ETHERNET COMMUNICATIONS SWITCH – INSTRUCTION MANUAL 3–9
6. Centralized DC power source cable securing; use at least four cable ties to
secure the cable to the rack at least 4 inches apart, with the first one located
within 6 inches of the terminal block.
7. For AC and HI powered units, use only with listed 20A circuit breaker provided
in building installation. Circuit breaker shall be provided in end system or
building as disconnect device.
3.4.3 Alarm Contacts
The alarm contacts feature provides two form-A normally closed (NC) contacts to which
the user can attach two 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 ML1600 case. The DC power input connection is in the same panel. A manual on-off
switch for power to the unit is not available on ML1600 units with the alarm contacts
option, as these two features occupy the same space in the case.
The first NC alarm contact (top position) is a “software alarm”, operated by user settings in
the ML1600 software. The user can disable the software alarm feature with a software
configuration command if desired. When the software alarm is enabled, the form-A
normally closed (NC) contact is held close during normal software operation. A user-
defined software malfunction, such as an SNMP trap or a software security violation or an
S-Ring Fault, causes the contact to open and thus trigger an alarm in the user’s monitoring
The second (bottom position) NC alarm contact is held close when there is power on the
main board inside of the ML1600. This provides a “hardware 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 ML1600 power supply. Useful information about the alarm
• The four terminal block (1, 2, 3, and 4) is adjacent to the power supply.
• The top two pins (1 and 2) are software operated.
• The bottom two pins (3 and 4) are hardware operated.
• By default, the alarm contacts are NC (normally closed).
• Software operation must be enabled to get the alarm traps. Further information is
provided in this manual.
The alarm contacts are on the front left area (next to the RS232 port) of the ML1600 unit.