The **FMS-3-R** is a specific electronic component, typically identified as a **Fast-Acting Subminiature Fuse** (specifically from the FMS series by manufacturers like SCHURTER). These are designed for primary protection on Printed Circuit Boards (PCBs). ### Technical Specifications The "R" suffix usually denotes **RoHS compliance** (Restriction of Hazardous Substances). Below are the core electronic characteristics: | Property | Specification | | :--- | :--- | | **Type** | Subminiature Fuse (Radial Leads) | | **Characteristic** | Fast-Acting (F) | | **Mounting Type** | Through-hole (THT) | | **Voltage Rating** | Typically 250 VAC / 125 VDC | | **Breaking Capacity** | 100 A @ 250 VAC | | **Body Material** | Thermoplastic (UL 94V-0) | | **Lead Material** | Tin-plated Copper | --- ### Key Electronic Components & Construction #### 1. The Fusible Element The heart of the FMS-3-R is a calibrated metallic wire or strip. - **Function:** It is engineered to melt when the current exceeds the rated value (3 Amps in this specific model). - **Response:** Being "Fast-Acting," it reacts quickly to short circuits, protecting sensitive downstream semiconductors. #### 2. Radial Lead Design The component features two parallel leads protruding from one side. - **Pitch:** Usually 5.08mm. - **Advantage:** Saves significant horizontal board space compared to traditional cylindrical glass fuses. #### 3. Housing (Encapsulation) The internal element is housed in a rectangular or square thermoplastic box. - **Protection:** This protects the element from environmental factors like oxidation and prevents arcing from escaping the component during a blow-out. --- ### Application in Circuitry The FMS-3-R is used in the following electronic contexts: * **Power Supplies:** Acts as a safety barrier at the AC input or DC output stages. * **Consumer Electronics:** Found in chargers, adapters, and small appliances. * **Industrial Controllers:** Protects PLCs and sensor interfaces from overcurrent. ```markdown # Circuit Symbol Representation F1 (3A) -----[ ~~~~ ]----- (Fuse) ```