The **MEH76XAD-R** typically refers to a high-capacity, heavy-duty **Electromagnetic Door Holder** (often manufactured by brands like RCI or similar hardware groups). These devices are integral components of fire safety and access control systems. Below is a detailed breakdown of its electronic parts and technical specifications. --- ## 1. Core Electronic Components The device operates on the principle of electromagnetism to hold fire doors open during normal operation and release them during an emergency. | Component | Description | Function | | :--- | :--- | :--- | | **Electromagnetic Coil** | Copper wire wound around a steel core. | Generates the magnetic field when energized. | | **Armature Plate** | A metal plate mounted to the door. | Attaches to the magnet to hold the door in place. | | **Internal PC Board** | Integrated circuit board. | Manages voltage regulation and surge protection. | | **MOV (Metal Oxide Varistor)** | Built-in surge suppressor. | Protects the system from voltage spikes/transients. | | **Terminal Block** | Screw-down wiring ports. | Provides points for power input (typically 12V or 24V). | --- ## 2. Technical Specifications These parts are designed to be "Fail-Safe," meaning they require constant power to stay locked. If power is cut (by a fire alarm), the door closes automatically via a door closer. ### Electrical Input The MEH76XAD-R is usually **Dual Voltage**, allowing for flexibility during installation: * **12V DC:** ~40mA Draw * **24V AC/DC:** ~20mA Draw * **120V AC:** (In specific models with built-in transformers) ### Holding Force * **Standard Force:** 25–40 lbs (11.3–18.1 kg). This is calibrated to hold the door firmly but allow for manual release (pulling the door shut) without damaging the electronics. --- ## 3. Wiring and Integration The electronics are designed to interface directly with a building’s **Fire Alarm Control Panel (FACP)**. ```mermaid graph LR A[Power Supply] --> B[Fire Alarm Relay] B --> C[MEH76XAD-R Magnet] C -- Magnetic Field -- D[Armature Plate on Door] ``` ### Wiring Steps: 1. **Selection:** Set the jumpers/switches on the internal PCB to match the site voltage (12V or 24V). 2. **Connection:** Connect the positive and negative leads to the terminal block. 3. **Grounding:** Ensure the backbox is properly grounded to prevent static interference with the coil. --- ## 4. Maintenance of Electronic Parts * **Residual Magnetism:** The armature plate usually features a spring-loaded pin to overcome "residual magnetism," ensuring the door drops immediately when power is cut. * **Alignment:** The electronic efficiency depends on the physical contact between the magnet face and the armature. Misalignment increases current draw and reduces holding force.