### Technical Overview: XT09-4EI-R The **XT09-4EI-R** is a high-performance 900 MHz stand-alone radio modem manufactured by Digi International (formerly MaxStream). It is designed for long-range serial communication in industrial environments. --- ### Core Specifications The following table highlights the primary electronic and operational characteristics of the device: | Feature | Specification | | :--- | :--- | | **Frequency Range** | 902 - 928 MHz (ISM Band) | | **Interface** | RS-232 / RS-485 (Switch selectable) | | **Output Power** | 100 mW (20 dBm) | | **Indoor Range** | Up to 1500 ft (450 m) | | **Outdoor Range** | Up to 7 miles (11 km) with high-gain antenna | | **Data Rate** | 9.6 kbps or 19.2 kbps | | **Operating Voltage** | 7V - 28V DC | | **Current Consumption** | 110 mA (TX), 30 mA (RX) | --- ### Key Internal Electronic Components The device is composed of several critical subsystems that manage power, signal processing, and communication: 1. **Transceiver IC**: The heart of the unit, utilizing **FHSS (Frequency Hopping Spread Spectrum)** technology. This allows the device to switch frequencies rapidly to minimize interference and bypass obstructions. 2. **Microcontroller**: Manages the onboard buffer, handles AT commands for configuration, and controls the data flow between the serial port and the RF stage. 3. **Interface Bridge**: An industrial-grade level shifter that converts logic-level signals to **RS-232** or **RS-485/422** standards. 4. **Voltage Regulator**: A wide-input switching regulator that allows the device to be powered by standard industrial power rails (typically 12V or 24V) without overheating. --- ### Physical Connectivity The "4EI" designation in the model number typically refers to the specific enclosure and interface configuration: * **RS-232 Port**: DB-9 female connector for standard PC or PLC connection. * **RS-485/422**: Terminal block or specific pins for multi-drop networking. * **Antenna Port**: RPSMA (Reverse Polarity SMA) connector for attaching a swivel whip or external high-gain antenna. * **LED Indicators**: * **Power**: Indicates the unit is receiving DC voltage. * **TX/RX**: Flashes during data transmission or reception. * **RSSI**: Indicates Received Signal Strength. --- ### Configuration Example To configure the device via a terminal emulator (like XCTU or PuTTY), you use standard Hayes AT commands. ```bash # Entering Command Mode +++ # Expected response: OK # Read Channel Number ATHP # Returns current hopping channel # Set Destination Address ATDT 1234 # Sets the address of the radio to communicate with ```