The **21EN75-R1** is a high-performance, environment-sealed **limit switch** manufactured by Honeywell under the MICRO SWITCH™ EN series. These components are specifically designed for critical applications where reliability in extreme environments is mandatory. --- ### 1. Core Technical Specifications | Feature | Specification | | :--- | :--- | | **Actuator Type** | Top Plunger (Stainless Steel) | | **Circuitry** | SPDT (Single Pole Double Throw) | | **Current Rating** | 4 Amps (Resistive) at 28 VDC | | **Housing Material** | Stainless Steel | | **Sealing** | Environmentally Sealed (Resilient Seal) | | **Termination** | Lead Wire (Military Standard) | | **Operating Temperature** | -54°C to 85°C [-65°F to 185°F] | --- ### 2. Key Electronic and Mechanical Parts #### A. The Micro Switch Internal Mechanism At the heart of the 21EN75-R1 is a precision snap-action switch. This mechanism ensures that the transition between "Open" and "Closed" circuits happens almost instantaneously, regardless of the speed at which the plunger is pushed. This prevents arcing and reduces wear on the electrical contacts. #### B. The Housing and Sealing * **Stainless Steel Enclosure:** The exterior is built from rugged stainless steel to resist corrosion and physical impact. * **Environment Proofing:** The "EN" series features a specialized seal that prevents dust, water, oil, and ice from entering the switching chamber. This makes it suitable for high-altitude or submerged conditions. #### C. Electrical Contacts The contacts are typically plated with high-conductivity materials (often gold or silver alloys) to ensure low electrical resistance. In the 21EN75-R1, these are rated for **4 Amps**, which is sufficient for signaling control units or triggering small relays. --- ### 3. Application Use-Cases Due to its military-grade construction (often meeting MIL-PRF-8805 standards), this part is commonly used in: * **Aerospace:** Landing gear position sensing, cargo door latches, and flap limits. * **Defense:** Armored vehicle hatches and weapon system interlocks. * **Marine:** Deck equipment and valve positioning in salt-spray environments. --- ### 4. Wiring Diagram Representation The device functions as a standard SPDT switch: ```text Terminal 1 (Common) -------+ | o (Normally Closed) --- Terminal 2 \ \ (Snap Action) \ o (Normally Open) --- Terminal 3 ```