The **RJS125-R** is a specific type of **radial leaded micro fuse** manufactured by **Bel Fuse Inc.** It is designed for board-level overcurrent protection in telecommunications, computing, and industrial applications. --- ## 1. Core Technical Specifications The "RJS" series is characterized by its rectangular, compact plastic body and long leads for through-hole mounting. | Feature | Specification | | :--- | :--- | | **Component Type** | Radial Leaded Micro Fuse | | **Current Rating** | 1.25 Amperes (1250 mA) | | **Voltage Rating (AC)** | 600V AC | | **Voltage Rating (DC)** | 600V DC | | **Response Characteristic** | Fast Acting / Slow Blow (Series dependent, check suffix) | | **Interrupting Rating** | 60A @ 600V AC | | **Material** | Thermoplastic (UL 94V-0) | | **Lead Finish** | Matte Tin-plated Copper | --- ## 2. Key Features and Construction The RJS125-R is engineered for space-constrained environments where traditional glass tube fuses are too large. ### A. Physical Design * **Form Factor:** The fuse features a rectangular body with two parallel wire leads protruding from the bottom. * **RoHS Compliant:** The "-R" suffix at the end of the part number signifies that the component is **RoHS compliant** (Lead-Free). * **Mounting:** Designed for Through-Hole Technology (THT) on Printed Circuit Boards (PCBs). ### B. Protection Mechanism * **Thermal Trip:** The internal element melts when current exceeds 1.25A for a sustained period, breaking the circuit to protect downstream components. * **High Voltage Rating:** One of the standout features of this specific part is the **600V** rating, which is significantly higher than standard 250V micro fuses. --- ## 3. Common Applications Due to its high voltage rating and compact size, the RJS125-R is frequently found in: * **Telecommunications:** Protection for modems, routers, and line cards against power surges. * **Power Supplies:** Used in the primary or secondary side of AC/DC converters. * **Lighting:** Ballasts and LED drivers. * **Smart Meters:** Grid-connected monitoring devices requiring compact protection. --- ## 4. Typical Part Number Breakdown Understanding the nomenclature helps in selecting the correct variant: | Part Segment | Meaning | | :--- | :--- | | **RJS** | Series Name (Radial Jacketed Short) | | **125** | Current Rating (1.25 Amps) | | **-R** | RoHS Compliant / Lead-Free |