The good Seal bug, often called "The Point" – one of many very first passive covert listening gadgets; 1st employed by the USSR for spying (1945 or previously); it is considered a predecessor of RFID technologies[fifty two] The mixer produces the audio-array difference between the frequencies of The 2 oscillators https://arthurhdtmc.free-blogz.com/85634719/a-review-of-mezzanine-gate