The **MF-RX012/250-2** is a specialized electronic component known as a **Resettable Fuse** (or PPTC: Polymeric Positive Temperature Coefficient device). It is manufactured by Bourns and is specifically designed for telecommunications and high-voltage protection applications. --- ## 1. Technical Specifications | Parameter | Value | | :--- | :--- | | **Hold Current ($I_{hold}$)** | 0.12 A (120 mA) | | **Trip Current ($I_{trip}$)** | 0.24 A (240 mA) | | **Maximum Voltage ($V_{max}$)** | 60V (Operating) / 250V (Interrupt) | | **Maximum Current ($I_{max}$)** | 3.0 A | | **Mounting Type** | Through-Hole (Radial Lead) | | **Packaging** | Tape & Reel (indicated by the "-2" suffix) | --- ## 2. Key Features and Operation ### How it Works Unlike a traditional fuse that "blows" and must be replaced, this PPTC device acts like a variable resistor. 1. **Normal State:** Under normal current levels, the device maintains a very low resistance. 2. **Fault State:** When an overcurrent or short circuit occurs, the internal polymer heats up rapidly, causing its resistance to spike. This effectively "opens" the circuit. 3. **Reset:** Once the power is removed and the device cools down, it returns to a low-resistance state and resets automatically. ### High Voltage Tolerance The **/250** in the part number signifies its ability to withstand power cross and lightning surge tests. It is rated for an interrupt voltage of **250V**, making it suitable for equipment connected to AC power lines or telephone systems. --- ## 3. Applications * **Telecommunications:** Protecting line cards and customer premise equipment (CPE). * **Industrial Controls:** Protecting sensors and low-current control circuits from wiring errors. * **Smart Meters:** Overcurrent protection in utility metering. * **Safety Agency Compliance:** Often used to meet ITU-T K.20/K.21 and Telcordia GR-1089 standards. --- ## 4. Part Number Breakdown * **MF-RX:** Multifuse® Resettable Fuses (Radial Lead series). * **012:** Hold current of 0.12 Amps. * **250:** Indicates high voltage (250V) capability. * **-2:** Tape and Reel packaging for automated assembly.