Altronix AL400ULB 12/24VDC Power Supply Charger Board
The Altronix AL400ULB is a dual-voltage power supply and charger board purpose-built for access control, burglar alarm, and fire alarm systems. It accepts 24/28VAC input and delivers either 12VDC or 24VDC output (user-selectable), making it suitable for mixed-voltage security infrastructure. The board integrates battery charging, supervision circuitry, and a fire alarm disconnect relay — reducing the need for separate components in retrofit or new installations.
Key Features
- Selectable 12VDC or 24VDC Output: Choose voltage post-installation to match your access control readers, door locks, alarm sensors, or other downstream devices without board swap. Eliminates guesswork during planning phases.
- 4A @ 12VDC or 3A @ 24VDC Main Supply: Adequate headroom for multi-door access control nodes, alarm panels with extensive wiring, and small battery banks. The 0.75A battery rail supports concurrent charging even under load on the main output — typical of professional security gear.
- Integrated Battery Charging Circuit: Built-in charger means no separate battery management board required, reducing board real estate and cost of goods in cabinet builds. Supports supervised backup operation — power doesn't silently fail.
- Fire Alarm Disconnect Relay: Complies with UL1481 fire alarm protocol requirements. The relay de-energizes non-fire loads during alarm state, ensuring alarm circuits retain priority power.
- AC Fail Detection: Triggers when main power drops. Integrates with existing supervision loops — you know instantly if your AC source fails, not after the fact.
- Low Battery and Battery Presence Monitoring: Supervision signals tell you if the backup battery is depleted or disconnected before a real outage. Prevents silent single-points-of-failure.
- UL Recognized Component: Meets UL294 (Access Control), UL603 (Burglar Alarm), and UL1481 (Fire Alarm) — all three in one device. Simplifies code compliance documentation for integrators and end-users alike.
- Compact Board Footprint: 7.05" × 4.05" × 1.6" board fits standard 10" × 8" × 4" enclosures, leaving room for additional modules, terminal blocks, or relays without oversizing the cabinet.
Integration & Compatibility
The AL400ULB works downstream of any 24/28VAC transformer or signaling line extra-low voltage (SELV) source. It pairs well with access control panels, burglar alarm system power supplies, fire alarm initiating device circuits, and battery backup systems in hybrid or retrofit deployments. Supervision output pins integrate directly into existing alarm loops or digital I/O on compatible control panels. If your cabinet runs mixed 12V and 24V buses, the selectable output eliminates the need for separate regulators.
Typical Deployment Scenarios
Multi-Tenant Access Control: Tenants on the same floor may need different reader voltages. Install one AL400ULB and configure outputs per tenant node without rewiring.
Burglar + Fire Alarm Hybrid: Fire alarm takes priority via the disconnect relay. Burglary circuits remain operational on supervised battery power during alarm state.
Retrofit Integrations: Existing 24VAC infrastructure can supply the AL400ULB. Selectable output voltage lets you add 12V subsystems (e.g., card readers, door sensors) without a second power supply.
Environmental & Warranty
Operating temperature range of 0°C to 49°C (32°F to 120°F) suits indoor cabinets and non-heated closets but not outdoor pedestals or uninsulated vaults. Lifetime Limited Warranty covers defects in materials and workmanship — typical of Altronix component products.
Frequently Asked Questions
Q: Can I use the AL400ULB with a 120VAC or 240VAC primary transformer?
A: No. The AL400ULB requires 24/28VAC input. You must use a control transformer rated for 24/28VAC secondary, or a 24/28VAC HVAC control power source. Connecting higher voltages will damage the board.
Q: Does the AL400ULB support remote supervision signaling?
A: Yes. AC fail, low battery, and battery presence outputs are available as supervisor signals. These can integrate into an alarm panel's input loop or a separate monitoring system, allowing centralized oversight of power status across multiple boards.
Q: What happens if the backup battery is connected but not charged?
A: The board will detect battery presence but signal low battery via the supervision output. Main output remains live from the AC source, but you'll receive an alert that backup power is insufficient. You should replace or recharge the battery before relying on it.
Q: Is the fire alarm disconnect relay normally-open or normally-closed?
A: The relay is normally-open under normal operation (main AC power present). On fire alarm signal or when AC fails, the relay energizes to de-energize non-fire loads, protecting alarm circuit power. Consult the datasheet for relay contact ratings and wiring.
Q: Can I configure different output voltages for different loads on the same board?
A: No. The AL400ULB delivers one voltage at a time — either 12VDC or 24VDC — selected once at installation. If you need both voltages simultaneously, you require two boards or a different power architecture.
Q: What is the maximum total load (main output + battery output) the AL400ULB can support?
A: Main outputs are 4A @ 12VDC or 3A @ 24VDC. Battery output is rated 0.75A @ 12VDC. Total current from the AC source cannot exceed the main rail rating. Battery rail is independent and supports charging during main output draw, but you must respect the 0.75A limit on battery-powered devices.
Ted PerryPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
The AL400ULB is the right tool when you need power supervision and battery charging rolled into a single board. I've seen too many retrofit jobs fail because the integrator cobbled together separate 12VDC and 24VDC supplies, missed the battery charger entirely, and had no way to know when AC failed. The AL400ULB prevents that. The dual-voltage selectability cuts down on SKU sprawl during job design, and the fire alarm disconnect relay removes a whole class of integration mistakes — no more accidentally powering non-essential loads during an alarm state.
Technical Highlights:
- 4A @ 12VDC or 3A @ 24VDC output: Sufficient for a 4-door access control node plus sensors without derating. The independent 0.75A battery rail lets you charge a backup battery while main loads run — no voltage sag when charging begins.
- Integrated supervision (AC fail, low battery, battery presence): Three discrete outputs that tie straight into existing alarm loops or digital inputs. You know the state of your backup power before an outage, not after — a genuine operational advantage in mixed-system deployments.
- Fire alarm disconnect relay: Automatic load shedding on alarm state. Eliminates the need for an external relay and wiring to implement UL1481 compliance — the cost and labor savings add up fast on large deployments.
- Compact 7.05" × 4.05" form factor: Fits in standard 10" × 8" × 4" enclosures with room to spare. I've never struggled to fit this board into a cabinet alongside existing relays or terminal blocks.
Deployment Considerations:
- The 0°C to 49°C operating range means this is an indoor-only, climate-controlled product. Don't spec it for unheated cabinets or outdoor pedestals — high or low temperature excursions will shorten its life.
- Output voltage is one-time selectable at installation. If your job changes mid-build and you suddenly need both 12V and 24V on the same board, you can't reconfigure — you need a second board. Size your cabinet power architecture early.
- The fire alarm disconnect relay is not a full 24VDC industrial relay — check the datasheet for contact load specs. On heavy loads (e.g., multiple door strikes), you may need an external contactor downstream of the AL400ULB's relay output.
- Supervision outputs are voltage signals, not relays. If your control panel needs contact closures for AC fail or low battery alerts, you must use an external relay or digital input module — the AL400ULB alone won't drive an electromechanical alarm bell or solenoid.
The AL400ULB shines in hybrid burglar/fire/access control retrofits and multi-tenant buildings where voltage flexibility matters. It's not a replacement for enterprise-grade power conditioning (no surge suppression, no RFI filtering), but as a cabinet-mounted SELV regulator and charger, it eliminates single points of failure and simplifies integration logic. Pair it with a properly sized 24VAC transformer and a quality sealed lead-acid or lithium battery, and you have a rock-solid backup power platform that passes code audit and survives real-world power events.
