Nortel Networks 3500, NTRN10AN manual Power Input Alarm, Breaker Alarm, Bay Alarms, Alarm Circuits

Hardware feature descriptions 3-43

Power Input Alarm

This circuit detects input power failure. A green light “on” indicates normal operation. If input power has been lost, this light is off. In normal operation, the power input alarm external relay contacts are in an energized or powered state. The contacts are in a deenergizing or powered-off state when input power is lost, providing C to NC closure for the alarm state.

Breaker Alarm

Breaker alarms operate in one of two ways. Both methods have a red indicator light “off” for normal operation and “on” when the alarm circuit is activated.

The first method uses indicating type breakers that provide a mechanical connection to activate the alarm card. The second method uses open-circuit electronic sensing across the fuse holder. Open-circuit detection usually requires a reset switch to clear the breaker alarm.

Both methods have the breaker alarm external relay contacts deenergized or in a powered-off state for normal operation and energized or in a powered-on state when a breaker alarm is detected, providing C to NO closure for the alarm state.

Bay Alarms

Bay alarms are visual indications for the rack frame (system level). These alarms can be a combination of three different levels: critical, major, and minor. Critical alarms are red; a major alarm can either be a red or yellow; and the minor alarm is always yellow. The external alarm contacts are deenergized or in a powered-off state for normal operation and energizing or going to a power-on state when an external alarm is detected. Activation of these types of alarms comes from external equipment alarm contacts that are either in the rack frame or system and provide an alarm ground to the input ports of the alarm system.

Alarm Circuits

Most monitoring alarm systems require an alarm ground signal to activate the individual alarms.

The most common, is a single-point contact or paralleled contact configuration. An alarm ground wire connects to the common of the external relay contact, and the associated NC or NO contact connects to the alarm monitoring system. When the alarm activates, the relay closure between the C and either the NC or NO sends an alarm ground to the alarm monitoring system, activating the appropriate alarm. Multiple relay contacts can be paralleled in this configuration to activate a single or multiple input to the alarm monitoring system.

Planning and Ordering Guide—Part 1 of 2 NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004