Insert a GSM SIM card into the slot and put the audio bug at hidden place,then dial the card number to monitor your target,you will hear the sound arround the bug.(5-15m range) This cool spy gadgets looks like a normal car key,noboby will know it is a audio bug there.

Specification 

    * Frequency: GSM 900/1800/1900MHz
    * Power Supply: Rechargable Li-battery
    * Transmission Distance: Non-limit
    * Card Compatible: GSM sim card
    * Receive Sensitivity:  ±10K
    * Stand-by Time: 7 days
    * Working Time: 4 hours
    * Sensitive Range: 5-15m
    * Product Dimensions: 50x40x25mm
    * Working  Temperature: -40℃ to 50℃
    * Accessories: AC adapter,USB cable