For more than 45 years now, PKI has been developing audio surveillance equipment. In particular, the latest achievements in the digital sector during the last 12 months must be highlighted. This applies especially to stethoscopes and directional microphones. One reason for this is the growing demand as the excellent PKI quality in this respect has become wider known at the international ministries. Another reason is the easy handling that is necessary to get important information and the fact that the stethoscope can be pressed on a wall, door or window using the PKI mastic material and is self-adhesive. PKI 2400 penetrates all these materials and records even the smallest acoustic signals, amplifies them up to 60,000 times and forwards these digital signals wirelessly up to 200m to a miniature receiver where they are replayed on the earphones. The surveillant can move freely and does not need to be in the immediate vicinity of the stethoscope, as was previously the case. This new PKI technology virtually eliminates the risk of discovery. There is nothing better and easier. The intercepted conversations can on request be recorded with our PKI 2105 Recorder for hours. On request, the receiver unit can also record completely automatically without any person being present. This again reduces the risk of discovery during an audio surveillance operation. PKI would like to submit a corresponding quotation on request.