The **ALR-122-R** is a specific model of an **Outdoor Photocontrol** (often referred to as a "NEMA twist-lock photocell") commonly used for street lighting and outdoor area illumination. It is designed to automatically turn lights ON at dusk and OFF at dawn. Below is a breakdown of its electronic components and technical specifications. --- ### 1. Key Electronic Components | Component | Function | | :--- | :--- | | **Cadmium Sulfide (CdS) Cell** | The light-sensitive sensor (photoresistor) that detects ambient light levels. | | **Bimetal Thermal Switch** | Acts as the physical relay. When the sensor detects darkness, current flows to heat the bimetal strip, which bends to close the circuit. | | **MOV (Metal Oxide Varistor)** | Provides surge protection against lightning strikes or grid voltage spikes. | | **Internal Heater** | Used in conjunction with the bimetal strip to create a "time delay" (preventing flickering from car headlights). | --- ### 2. Technical Specifications The ALR-122-R follows industry standards for municipal and commercial lighting. * **Operating Voltage:** 105-130 VAC (50/60 Hz). * **Load Rating:** * 1000 Watts Tungsten. * 1800 VA Ballast. * **Turn-On Threshold:** 1 to 3 footcandles (fc). * **Turn-Off Ratio:** Typically 1:5 ratio (Turns off when light is significantly brighter than the turn-on point). * **Connection Type:** 3-prong NEMA twist-lock (ANSI C136.10 compliant). --- ### 3. Operational Logic 1. **Detection:** As daylight fades, the resistance in the **CdS cell** increases. 2. **Delay Mechanism:** The device utilizes a thermal delay (usually 30–60 seconds). This ensures that brief flashes of light (like lightning or a passing car) do not turn the streetlamp off. 3. **Fail-Safe:** Most models in this series are designed to fail in the **ON position**. If the internal sensor or circuit fails, the light stays on during the day, signaling to maintenance crews that the unit needs replacement. --- ### 4. Physical Construction * **Housing:** UV-stabilized polypropylene cover (usually translucent or blue). * **Base:** Heat-resistant phenolic base. * **Gasket:** Cross-linked polyethylene to prevent moisture ingress.