Altronix AL125ULB Dual-Output 12/24VDC Power Supply Board
The Altronix AL125ULB is a compact board-form AC/DC power supply and battery charger designed for low-voltage access control, emergency lighting, and fire alarm circuits. It accepts a standard 24VAC 40VA input transformer and delivers two independent output channels, each selectable for 12VDC or 24VDC operation at 1A per channel. Built-in supervised fire alarm disconnect functionality with latching or non-latching modes integrates seamlessly into systems requiring monitored power and backup battery support for unsealed lead acid or gel-type batteries (sold separately).
Key Features
- Dual independent outputs: Each channel rated for 1A, selectable between 12VDC or 24VDC — lets you run mixed-voltage devices from a single board without separate power supplies.
- Integrated battery charger: Supports sealed lead acid or gel-type backup batteries, ensuring uninterrupted operation during AC power loss — critical for access control and emergency systems that cannot tolerate downtime.
- Supervised fire alarm disconnect: Latching or non-latching modes let you configure automatic or manual reset behavior when disconnect is triggered — meets NFPA 101 Life Safety requirements for monitored power circuits.
- PTC-rated overcurrent protection: 2.5A per-output protection prevents cascading failures if a connected device draws excessive current; automatic reset eliminates the need to swap fuses.
- LED status indication: Four distinct states (Normal, No Output, Loss of AC, Triggered) provide at-a-glance visibility into power and alarm status — reduces troubleshooting time during maintenance or fault response.
- UL Listed, Class 2 transformer-based design: UL recognition and NFPA 101 compliance mean the AL125ULB satisfies code requirements for life safety applications; Class 2 operation means safe low-voltage distribution without additional isolation measures.
Power & Input Specifications
The AL125ULB draws 24VAC at 40VA input — a standard transformer-secondary voltage available on most commercial power distribution systems. This modest input load means it integrates easily into existing low-voltage wiring runs without requiring dedicated supply transformers. Output capacity is 1A per channel; the PTC overcurrent element is rated 2.5A, providing a safety margin that allows brief surge currents during access control solenoid energization without nuisance trips.
Form Factor & Installation
Measuring 3.8" × 3.0" × 1.5", the board-form design fits into standard DIN rail enclosures or compact cabinet spaces — valuable when mounting space is limited. Its compact footprint makes it suitable for retrofit installations in existing fire alarm or access control cabinets where larger modular supplies won't fit. Operating temperature range of 0°C to 49°C (32°F to 120°F) covers most indoor commercial environments; for heated or unheated mechanical rooms, confirm the ambient temperature stays within this window.
Battery Backup & Supervised Disconnect Integration
When AC power fails, the integrated charger maintains a standby battery (specified by the system designer) in a charged state, ready to power access control locks, door strikes, and other critical loads. The supervised fire alarm disconnect function monitors the power state and can trigger an alarm signal to the fire panel or building management system when AC is lost or when the disconnect function is manually activated — essential for facilities where loss of emergency power must be logged and reported.
Warranty & Support
The AL125ULB includes a Lifetime Limited warranty, reflecting Altronix's confidence in the transformer-based design and component selection. For integration questions or application-specific configuration, consult the product datasheet or work with your integrator.
When to Choose a Different Model
If your system requires higher per-channel current (above 1A continuous), or if you need more than two independent output circuits, consider other power supply options in the Altronix low-voltage power family. Systems requiring remote monitoring or SNMP-based status reporting may benefit from switched power products with network connectivity.
Frequently Asked Questions
Q: What type and capacity of backup battery does the AL125ULB support?
A: The AL125ULB integrates a battery charger for sealed lead acid (SLA) or gel-type batteries. You select the battery capacity (measured in amp-hours) based on your runtime requirement during AC loss. The board itself imposes no hard limit on battery size, but consult the datasheet for recommended AH ranges and charge current specifications.
Q: Can I run both outputs at 24VDC, or are they forced to different voltages?
A: Each output channel is independently selectable for 12VDC or 24VDC via terminal jumpers or configuration. You can run both at 24VDC, both at 12VDC, or one at each voltage — the configuration is user-selectable during installation.
Q: Is the AL125ULB suitable for outdoor fire alarm distribution cabinets?
A: The AL125ULB itself is rated for 0°C to 49°C operation. Outdoor cabinets with poor thermal management or extreme temperature swings may exceed this range. Always mount the board inside a temperature-controlled enclosure or cabinet with adequate ventilation.
Q: What is the maximum current draw if both outputs are used simultaneously?
A: Each output is rated 1A continuous. Maximum combined draw is 2A (1A + 1A). The PTC overcurrent element is rated 2.5A per output, so you have some headroom for brief inrush currents, but sustained loads above 1A per channel will risk nuisance trips.
Q: Does the AL125ULB require a separate enclosure, or can it mount directly to a DIN rail?
A: The AL125ULB is a board-form module. It must be mounted inside a cabinet or enclosure — it is not a standalone, enclosed power supply. Install it in a standard DIN rail enclosure, control cabinet, or panel designed to house Class 2 low-voltage equipment.
Ted PerryPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
The AL125ULB is a workhorse board-form supply for fire alarm and access control circuits that need monitored power and battery backup in a footprint small enough to fit retrofit control cabinets. The dual independent 1A outputs with selectable voltage make it flexible for mixed-device deployments, and the integrated supervised disconnect function is a genuine convenience — you're not bolting on a separate monitoring relay. UL Listed status and NFPA 101 compliance mean code authorities won't question it.
Technical Highlights:
- 24VAC 40VA input: Standard transformer-secondary voltage — no special power infrastructure needed. The modest input load makes retrofit installations into existing power distribution practical.
- Integrated battery charger: Eliminates the need for a separate charger module. The board maintains backup readiness and delivers power during AC loss, reducing single points of failure in emergency systems.
- Supervised fire alarm disconnect with dual modes: Latching mode logs and holds a disconnect event until manually reset; non-latching mode resets automatically when the fault clears. Both modes report to the fire panel, meeting NFPA logging requirements.
- PTC-rated 2.5A overcurrent per output: Automatic reset eliminates manual fuse replacement and tolerates brief solenoid inrush (door strike pulls on access control systems) without nuisance disconnection.
Deployment Considerations:
- The AL125ULB is a board, not an enclosed supply — it must live inside a cabinet or control enclosure. Plan for DIN rail mounting space and ensure ambient temperature stays 0–49°C. Outdoor or unheated mechanical spaces often exceed this ceiling.
- Each output is rated 1A continuous. If a single load (a powerful electronic lock or solenoid, for example) draws more than 1A sustained, you'll need a higher-capacity supply from the Altronix family — don't underrate the circuit.
- Battery capacity is application-specific and not included. A 5AH SLA battery might give you 5 hours of standby at 1A draw; larger AH ratings extend runtime proportionally. Size based on your facility's emergency hold-time requirements and local codes.
Best suited for access control and fire alarm cabinet retrofits where space is tight, code compliance is non-negotiable, and you want intelligent supervised disconnect behavior built into the supply rather than bolted on as an afterthought. Not the right choice if you need more than 2A total output or outdoor, unheated mounting.
