The term **122-R** typically refers to a specific resistance value or a part marking found on Surface Mount Device (SMD) resistors. In the context of electronic components, "122" is the standard EIA (Electronic Industries Alliance) marking code. ### 1. Decoding the Value: 122 The three-digit code on an SMD resistor is read as follows: * **First Digit (1):** The first significant figure. * **Second Digit (2):** The second significant figure. * **Third Digit (2):** The multiplier (number of zeros to add). | Part Code | Resistance Value | Calculation | | :--- | :--- | :--- | | **122** | 1,200 Ohms ($1.2k\Omega$) | $12 \times 10^2$ | --- ### 2. The "R" Suffix Meaning In electronics, the letter **"R"** serves two primary purposes depending on its placement: #### A. Decimal Point Placement If the "R" is placed within the numbers (e.g., `1R22`), it acts as a decimal point ($1.22\Omega$). However, when it appears as a suffix (like **122-R**), it usually indicates: 1. **RoHS Compliance:** The part is Lead-Free and meets environmental standards. 2. **Packaging Style:** Often denotes "Reel" packaging for automated assembly. 3. **Tolerance/Series:** In some manufacturer-specific catalogs (like Eaton or Bussmann), it denotes a specific series of power inductors or fuses. --- ### 3. Common Component Types If you are looking for a specific part labeled "122-R," it most likely belongs to one of these categories: | Component | Example Manufacturer | Description | | :--- | :--- | :--- | | **SMD Resistor** | Generic (Yageo/Vishay) | $1.2k\Omega$ resistor, usually in 0603 or 0805 size. | | **Power Inductor** | Eaton (Bussmann) | DR127-122-R (A $1200\mu H$ High power shielded inductor). | | **Chip Fuse** | Bel Fuse | A surface mount fuse with a specific current rating. | --- ### 4. Technical Specifications (Typical for 122-R Resistors) If this is a standard resistor, it typically follows these specs: * **Tolerance:** $\pm 5\%$ (standard for 3-digit codes). * **Power Rating:** Ranges from 1/16W (0402) to 1/4W (1206) depending on physical size. * **Temperature Coefficient:** Usually $\pm 100ppm/^\circ C$ to $\pm 200ppm/^\circ C$.