Sometimes a room is only accessible via tiny holes or cracks, where only a needle microphone is small enough to be introduced and to capture conversations from inside the room. The signals are amplified by the integrated amplifier, so that direct listening via headphones is possible. The PKI 2470 Needle Microphone with Amplifier is equipped with an input socket for our digital recorder PKI 2105. Sounds are electronically adjusted, which means that low sounds are more amplified than louder sounds, so that the volume is maintained at a constant level.