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ITGlossary · Communication and monitoring
Alarm Contact
A relay output on a UPS that changes state on an alarm, such as battery mode, low battery or a fault, to alert an external system.
Technical level:Intermediate
An alarm contact lets a UPS or monitoring device "talk" to other systems without a network or software. When an event occurs, such as running on battery, low battery or a fault, the relay changes state and the signal can be wired to an alarm panel, building management system (BMS), PLC or a simple indicator lamp.
It is especially useful at remote or unattended sites, such as telecom stations and pumping stations, where someone must be notified immediately. Many UPS units offer such contacts through an optional expansion card.
Practical tip: where possible, use a normally closed (NC) contact. That way a cut cable also shows up as an alarm instead of going unnoticed.
Related terms
- Charging Modes (Mode 1–4)The IEC 61851 classification of EV charging, from a plain socket with no communication (Mode 1) to a DC fast charger (Mode 4).
- Dry ContactA passive relay contact used to transmit status signals without applying voltage.
- Shutdown SoftwareSoftware that talks to the UPS and automatically shuts down servers and computers safely before the battery runs out.
- Battery Management System (BMS)A system that monitors and manages the performance, health, and charging of batteries.
- DC EfficiencyMeasures how effectively a UPS converts battery power into output power during battery mode.
- Equalising ChargeA controlled charge at a higher than normal voltage that brings all cells of a lead-acid battery to the same state of charge.