A senior weak electrician will tell you something. In fact, before radio frequency identification technology was laid down by Soviet inventor Leon Theremin, all monitoring equipment could not get rid of the contradiction between lines and energy. Theremin laid down the foundation of radio frequency identification technology roughly around 1945, so it was impossible to have a bug that did not use wires or batteries during World War II.
Talking about technology also talks about history
We have generally learned something in middle school physics. The transmission of sound is essentially vibration, so the technical threshold for sound collection is not high, let alone the Anti-Japanese War. During the First World War, it was possible to achieve this by collecting vibrations through directional copper plates without directly connecting them.
In 1916, German engineers often climbed out of trenches late at night and buried about a square foot of copper plates underground, in mines or next to telephone lines, and then connected the copper plates to the "Moritz" listening device through the lines. Used to collect British military call information, that thing can easily restore vibrations to sounds.
In fact, American Kelly Turner obtained an invention patent for this type of technology as early as 1906 (Patent No. US843186A). The detective recorder he developed can record sounds remotely during interrogations ( Ability to record), and those recordings can be used as evidence in court.
The real threshold for monitoring during World War II was not sound collection, but transmission. Whether it was Turner's detective recorder or the German "Moritz", a large amount of wiring was required for transmission. Therefore, there are great limitations in high-end applications such as eavesdropping. If you want to eavesdrop, you must first invite that person into the room where you have finished wiring. But is that still eavesdropping?
Is it possible that some people will say that wired transmission is necessary? It’s not like there was no radio technology during World War II. Wouldn’t it be possible to use wireless transmission directly? Well, it's technically possible, but not in practical applications. The key point of radio is still the word "electricity". If you want to transmit the signal, you must first provide energy. At that time, battery miniaturization technology was not developed. You only need to install the battery to ensure that people can see it at a glance. , what should I do if the battery is dead?
So the author of the question thinks that bugs during the Anti-Japanese War were more advanced than now, probably because they were deceived by movies and TV shows. The commentators believe that those who stick a button-sized bug under the table can then use it in another place. The real-time monitoring equipment in the building did not exist, at least it did not exist in that era.
The breakthrough of "Golden Lips"
The technical barriers to transmission were actually only a few years old. On August 4, 1945, the Soviet Young Pioneers transferred a huge and exquisite wooden U.S. The national emblem was given to William Averell Harriman, then the U.S. Ambassador to the Soviet Union. Inside the national emblem was a groundbreaking listening device that hung in the embassy for seven years before it was discovered.
I don’t know why The Thing is translated as Golden Lips, but the principle of that thing is roughly the same as the bus card we often use. It consists of a high-sensitivity pickup and a capacitor through a cylindrical cavity resonator. Connected to the antenna, it has no power and does not emit electromagnetic waves. It is difficult to detect through instruments in the non-monitoring state.
But when the outside world gives the antenna a source wave that matches the capacitance, the eardrum in the pickup will react the vibration in the room to the antenna, and the source wave reflected back by the antenna will bring back the monitoring signal. , which can naturally be restored to sound after modulation. Sometimes I have to admit that Daxiong is quite good at doing detailed work seriously.
To sum up, the bugs during the Anti-Japanese War are not more advanced than modern times. They are just blind arrangements by directors who do not understand technology in film and television works. Even if they understand technology, it is impossible to act out the entire wiring process. The work definitely doesn’t look good, end of nonsense.