Victor HM-200 (JVC HM-200E) 3D Headphones + stereo binaural mic

Description

Victor HM-200 (JVC HM-200E) 3D Headphones + stereo binaural mic. Condition is good.
I sold 2 pieces of these headphones, but did not find a description, then there will be machine translation, I apologize.
Victor HM-200 or (JVC-200-E for Europe) combines 2 side microphones.  The angular placement of the microphones, as well as the design of the enclosure surrounding them, are designed to closely mimic the characteristics of the human ear.
Recordings made with the system produce a “3D” binaural effect, with sounds appearing to pass behind the listener, as well as from the front and sides, an effect reproduced on conventional stereo equipment and can be most convincing when wearing conventional stereo headphones.
An example of 3D binaural audio was recently recorded by the BBC (March 2, 2019).  Rob Da Bank used this technique specifically for headphones;
To achieve these recordings and for the best results, the headphones are traditionally attached to the styrofoam head ...
The microphones are powered by 2 AA batteries and have bass roll or full range of settings.
Playback can be set high, low, or off to control the risk of feedback.  Considering its age (produced in 1978-81) this specimen is in good condition and is in full working order.
The headphone jack is a 1/4 "stereo jack, and the microphones end on the left and right with 1/4" mono jacks.  If you prefer to replace them with XLR connectors, be sure to turn phantom power off to your recording equipment, as power is supplied by the AA batteries installed in the headset.
The world's first binaural headphone microphone that can be performed while monitoring binaural recordings.
The human ear has an accurate sense of direction and distance to sound.  This is done with both ears, and this effect is called binaural and is used to mean listening with both ears.  Sound reaching the human ear causes diffraction and resonance due to the presence of the head and turrets, and sound pressure, phase (time difference) and frequency characteristics differ from left to right.  Thus, human beings learn the difference, which changes with each angle of incidence, by experience, and judge the vertical and horizontal directions.  However, when using single focus microphones and multi-microphones, this directional information cannot be recorded.
Thus, it was believed that the reproduced sound is in the same state as when it was actually heard by the ear - it is a fictitious head (human oral) recording that is recorded and played back in the same position as the human ear.
The HM-200 was designed using a dummy head and has a structure in which the microphone is inserted into the earpiece itself, so that binaural recording can be easily performed.  In addition, with the development of a microphone built into the shape of the human ear headphones, it is possible to record the natural and natural feeling of human hearing more than that of a mannequin head.  Dummy head not included
This vintage machine allows access to the wonderful world of binaural recording, which is currently undergoing a revival.
Model binaural headphone microphone

format sealed type
Regeneration frequency range from 50 Hz to 10 kHz
Impedance 8 Ohm
Output SPL 96 dB
Low volume switching level: -10dB

format electret condenser type
SN ratio 45 dB or more
Output Impedance 600 Ohm
Frequency Response 50 Hz to 10 kHz ± 10 dB
Directional characteristics omnidirectional

code 2M
weight 460g