The designation **123-R** is frequently associated with specific electronic components, most notably high-precision resistors or specific semiconductors (like voltage regulators). Below is a breakdown of the most common electronic parts identified by this code. --- ## 1. High-Precision Resistors (MIL-SPEC / Industrial) In many electronic catalogs, `123-R` refers to a series of **Precision Wirewound Resistors**. These are designed for circuits requiring extreme stability and low tolerance. ### Key Specifications | Feature | Typical Value | | :--- | :--- | | **Tolerance** | ±0.01% to ±1% | | **Temperature Coefficient** | 2 ppm/°C to 10 ppm/°C | | **Power Rating** | 0.1W to 0.5W | | **Mounting Type** | Through-hole | --- ## 2. Voltage Regulators (NTE123 / NTE123-R) In the world of semiconductor replacement, "123" often refers to the **NTE123** series, which is a general-purpose Silicon NPN Transistor. ### Technical Characteristics * **Type:** NPN Silicon Transistor (often used for switching and amplification). * **Package:** TO-18 or TO-92. * **Collector-Emitter Voltage ($V_{ceo}$):** 40V. * **Collector Current ($I_c$):** 600mA. * **Common Use Cases:** 1. Small signal amplification. 2. High-speed switching. 3. Driver stages in audio equipment. --- ## 3. Surface Mount Device (SMD) Coding If "123" is printed on a small SMD resistor, it represents a specific resistance value based on the **three-digit EIA coding system**: ### Calculating the Value * **First two digits (12):** Significant figures. * **Third digit (3):** Multiplier (number of zeros). * **Result:** $12 \times 10^3 = 12,000 \Omega$ or **$12k\Omega$**. --- ## 4. Summary Table of Identification If you are looking at a part labeled "123-R", use this table to identify it: | Component Type | Meaning of "123-R" | Primary Function | | :--- | :--- | :--- | | **Resistor (SMD)** | $12k\Omega$ | Current limiting / Voltage dividing | | **Transistor (NTE)** | NPN Replacement | Signal switching and gain | | **Military Component** | Type 123, Revision R | High-reliability circuitry | ---