It helps to identify laser transmission direction and compare l aser transmission frequency. FEATURES: 1. Identify various kinds of signal frequency: 270Hz, 1kHz, 2kHz 2. Display optical transmission direction 3. Easy to remove and replace adapter 4. Low voltage indication 5. Automatic power off 6. Rechargeable Li battery 7. Small size, simple operation SPECIFICATIONS 1. Identify wave length range: 900~1,650nm 2. Identify signal type: CW, 270HZ±5% 3. Detector type: InGaAS 4. Sensitivity: -38dB@(1550nm) 5. Adapter Type:Ф250um:1.0dB, Ф90dm;0.5dB, Ф3mm:0.5dB 6. Communication signal indication: Direction indicator light & fitful buzzer 7. Signal intensity indication: 5 LED indication 8. Working temperature: 0~40°C 9. Storage temperature: -20~60°C 10. Relative humidity: 0~95%