Use the TRIG pin to trigger telemetry. The module requires at least 10 µs high-level TTL pulses. It automatically generates eight 40 kHz square wave pulses and detects returning signals. If a signal is received, it outputs a high-level TTL pulse on the ECHO pin. The duration of this high-level pulse corresponds to the time between transmission and echo reception. Distance is calculated as: (pulse duration × speed of sound (340 m/s)) / 2. Detection range: 2 cm to 450 cm. Accuracy: ±2 mm. Operating voltage: 5 V DC. Static current: ≤2 mA. Output signal: TTL-compatible; high level = 5 V, low level = 0 V. Beam angle: ≤15 degrees. Trigger input signal: 10 µs TTL pulse. Echo output signal: TTL pulse-width modulated (PWM) signal. Pin configuration: VCC (5 V power supply), TRIG (trigger input), ECHO (echo output), GND (ground). Package includes: 5 × HC-SR04 Ultrasonic Distance Sensor Modules for Arduino. Note: Measurements are manually taken; allow for ±1–3 cm tolerance. Color appearance may vary slightly due to lighting and display differences.