This serial breakout adapter provides safe and flexible TTL serial connections with visible status indicators and multiple power options. It is designed to protect connected devices from reverse polarity, while offering easy access to common signals and voltages. Key features Reverse connection protection with 500 mA resettable fuses to prevent damage if connections are made incorrectly. Three LEDs: TXD LED, LED, and POWER LED to show activity and power status at a glance. Output pins GND, TXD, 3V3, and 5V are provided with bent pins for reliable and easy wiring. Three power supply options: 5V external power supply; 3.3V external power supply; external power supply (3.3V5V required). Specifications and compatibility Provides GND, TXD, 3V3, and 5V outputs for flexible TTL serial connections. Supports external power supplies in the 3.3V to 5V range, including 5V and 3.3V options. Suitable for use with microcontroller development and debugging tasks requiring both 3.3V and 5V serial signaling. 23 practical use scenarios Serial communication with microcontroller boards: Use TXD and ground connections to communicate with boards operating at 3.3V or 5V, while powering the board from an appropriate supply and using the LEDs to monitor activity and power. Development and debugging: Connect to a target MCU or module to observe TXD activity and confirm power status during prototyping and testing, with the ability to switch between 3.3V and 5V as needed. Safe power and signal probing: Use the device to probe and power test setups where multiple voltage rails are required, reducing risk of reverse wiring and providing immediate status feedback via LEDs. Notes All specified signals and voltage outputs are designed for safe TTL level interfacing within the stated voltage ranges. External power supplies must conform to the 3.3V5V range as indicated.