Protected TTL serial interface with selectable voltage levels and multiple hardware protections Key benefits Prevents damage from electrical events: onboard IO protection circuit and TVS diode suppress surges and clamp transient voltages, reducing the risk of component failure. Flexible signal compatibility: selectable TTL serial port levels (3.3V and 5V) let you safely connect a wide range of TTL devices without levelshifting adapters. Reliable operation under fault conditions: resettable fuse protects against overcurrent and allows recovery after a fault, while backwardproof and ESD protection improve longterm reliability. Quick status checks: three LEDs clearly show power and TX/RX activity so you can verify connections and communication at a glance. Durable enclosure: a quality plastic case with a dullpolish surface provides a wellcrafted, professional finish and protects the internal circuitry. Features Onboard IO protection circuit for surge suppression TTL serial port with manual 3.3V / 5V voltage level switch Resettable fuse and TVS diode offering overcurrent, overvoltage, backwardproof, and ESD protection 3 × LED indicators for power and TX/RX status monitoring Quality plastic case with dullpolish surface Compatibility and performance Designed for TTLlevel serial communications; works with 3.3V or 5V TTL devices when the appropriate voltage is selected. Hardware protections maintain safe and stable communications in noisy or electrically active environments. Compact, enclosed design protects electronics while providing clear visual indicators for troubleshooting. Typical use scenarios Prototyping and development: connect microcontroller modules and TTL sensors during bench testing while protecting both the device and host from accidental surges or level mismatches. Field installations and industrial environments: improve robustness for serial links exposed to electrical noise, ESD, or occasional overcurrent events. Diagnostics and : monitor TX/RX activity and power status with LEDs while safely interfacing with TTLlevel equipment during troubleshooting. What makes this product stand out Integrated surge, ESD, and overcurrent protection in a single, compact module. Manual 3.3V/5V TTL selection avoids extra hardware and reduces risk of levelmismatch damage. Clear LED indicators and a sturdy plastic case for professional, reliable use in lab or field settings.