Landtek Instruments Professional Digital Sound Level Meter 30 to 130db with Bluetooth (Optional)               Standardisation: IEC651 Type 2, ANSI S1. 4 Type 2      PC interface: Bluetooth + CD Software (Optional , not included , cost USD50 extra , contact seller if needed)      Support WIN 8 ; Function: Lp, Leq, Lmax, LN. with Frequency range: 20.0 to 12,500Hz      Frequency range: 20.0 to 12,500Hz / Frequency weighting: A, C and F (Flat)      Alarm: electron, adjusable, 30-130dB set, LED and optional relay contact (NC) output      Built-in calibration signals: 94dB at 1kHz (sinusoidal)                    Product description     Great for noise pollution monitoring,factory,office,traffic, home theater setup,health and safety compliance,vehicle noise testing and audio system.     Features     Transfer data via Bluetooth connection     Filters-out unwanted signals     Bar graph & Over/under load Indication     A freq. weighting (general sound level measurements), C freq. weighting (checking low-frequency content of sounds)     AC/DC analog signal output for connecting to freq analyzer level recorder,FFT analyzer and graphic record     Factory pre-calibrated     Specifications     Measuring Level: 30-130dB(A), 35-130dB(C)     Level Range: 30-80dB ; 50-100dB ; 60-110dB ; 80-130dB ; 30-130dB     PC interface: Bluetooth+CD Software     Accuracy: +/-1.5dB (under reference conditions)     Resolution: 0.1dB     Range: 31.5Hz-8.5KHz (Frequency) ; 50dB/100dB (Linearity)50dB scale at 1dB step for monitoring current sound pressure level     Sample Rate: 20times/sec     Display: 4 digits     AC Signal Output: 0.707Vrms at FS output impedance approx. 600(ohm)     DC Signal Output: 10mV/dB, output impedance approx. 100(ohm)     Time Weight: FAST / SLOW     Mic: 1/2" Electronic Condenser mic     Max hold function     Environment 0-40°C, 10-80%RH (Operating) ; -10-60°C, 10-70%RH (Storage)     Power: 4xAA 1.5V alkaline batt (included) or DC 6V 100mA (max DC9V) (not incl.)     Batt Life: About 30hrs (alkaline batt)     Size: 256x70x35mm     Weight: 230g (excl. batt)     Set Includes     1 x Sound Level Meter     1 x Windscreen / Sponge Ball     1 x Shock Absorbent Carrying Case     1 x English Manual     1 x Standard Packaging Box          Optional Accessories (Contact Customer Service )                       (Optional , not included , cost USD50 extra , contact seller if needed)                1 x CD Software     1 x Bluetooth