Based on the part number structure, the **I641-61AB3O2-155.520** is a high-precision frequency control component, specifically an **OCXO (Oven Controlled Crystal Oscillator)**. These components are used in telecommunications and networking where extreme frequency stability is required. ### 1. Part Number Breakdown The alphanumeric code follows a specific naming convention used by manufacturers like *ILSI* or *MtronPTI*. | Segment | Feature | Description | | :--- | :--- | :--- | | **I641** | Series/Package | Indicates a standard 6-pin or 4-pin SMD package (often 14x9mm or similar). | | **61** | Supply Voltage | Usually denotes a **3.3V** DC operating voltage. | | **AB** | Stability/Temp | Represents the operating temperature range (e.g., -40°C to +85°C). | | **3O2** | Output Type | Indicates **LVPECL** (Low-Voltage Positive Emitter-Coupled Logic) output. | | **155.520** | Frequency | The fundamental frequency in MHz (**155.520 MHz**). | --- ### 2. Technical Specifications These parts are designed for "Stratum 3" or similar high-reliability timing applications. * **Center Frequency:** 155.520 MHz (A standard frequency for SONET/SDH and Optical Networking). * **Oscillator Type:** OCXO (Oven Controlled). It uses an internal heating element to keep the crystal at a constant temperature, preventing frequency drift caused by external temperature changes. * **Output Logic:** LVPECL. This provides high-speed switching with low jitter, ideal for clocking high-speed data buffers. * **Stability:** Typically measured in parts per billion (ppb) or parts per million (ppm), significantly more stable than standard XO or TCXO components. --- ### 3. Application Use Cases This specific frequency (155.520 MHz) is highly specialized for the following areas: 1. **Optical Networking:** Used in SDH (Synchronous Digital Hierarchy) and SONET (Synchronous Optical Networking) systems. 2. **Base Stations:** Providing the master clock for 4G/5G cellular infrastructure. 3. **Test & Measurement:** High-end oscilloscopes and signal generators requiring a stable reference clock. 4. **Data Centers:** Synchronization of high-speed switches and routers. --- ### 4. Comparison with Other Oscillators | Feature | XO (Crystal) | TCXO (Temp Comp) | **OCXO (I641 Type)** | | :--- | :--- | :--- | :--- | | **Stability** | Low (~50ppm) | Medium (~2ppm) | **High (0.01 - 0.1ppm)** | | **Power Consumption** | Very Low | Low | **High (due to internal heater)** | | **Warm-up Time** | Instant | Instant | **Required (seconds to minutes)** | | **Cost** | Low | Medium | **High** |