The **MJS 400-R** is a high-performance, subminiature surface-mount fuse manufactured by Bel Fuse. It is designed specifically for secondary circuit protection in compact electronic devices. --- ### ## Technical Specifications The "MJS" series stands for **Medium Slow-Blow** (Time-Delay) Square Surface Mount Fuses. Below are the primary electronic characteristics of the 400-R variant: | Feature | Specification | | :--- | :--- | | **Current Rating** | 400mA (0.4A) | | **Voltage Rating (AC)** | 125 VAC | | **Voltage Rating (DC)** | 125 VDC | | **Fuse Type** | Time-Lag / Medium Blow | | **Interrupting Rating** | 50A @ 125V AC/DC | | **Resistance (Cold)** | ~0.490 Ohms | | **Package / Case** | 2410 (6.10mm x 2.69mm) | | **Mounting Type** | Surface Mount (SMD/SMT) | --- ### ## Key Electronic Components & Materials The MJS 400-R is engineered with specific materials to ensure reliability under thermal stress: 1. **Ceramic Body:** The main housing is made of high-grade ceramic to withstand internal pressure and heat during a "blow" event. 2. **Gold-Plated End Caps:** The terminations are typically gold-plated (or silver-plated depending on the specific sub-series) to provide excellent conductivity and oxidation resistance during soldering. 3. **Fuse Element:** A calibrated metallic wire or strip designed to melt at a specific $I^2t$ (Ampere-squared seconds) threshold. 4. **Epoxy Coating:** Often features a UL 94-V0 rated flame-retardant coating for safety. --- ### ## Operational Characteristics * **Time-Delay (Medium Blow):** Unlike "Fast-Acting" fuses, the MJS 400-R is designed to ignore short-term current surges (inrush current) that occur when a device is first turned on. It will only trip if the overcurrent persists. * **RoHS Compliance:** The "-R" suffix indicates that the part is fully **RoHS Compliant**, meaning it is lead-free and environmentally friendly for global manufacturing standards. * **Safety Approvals:** It is generally UL (Underwriters Laboratories) recognized and CSA certified, ensuring it meets industrial safety standards for overcurrent protection. --- ### ## Typical Applications Due to its small footprint and time-delay nature, it is commonly used in: * LCD Monitors and TV backlighting. * Power supplies for laptops and tablets. * Medical electronic equipment. * Industrial control boards where space is limited.