The polarized signal is recovered from the first harmonic at 40 kHz using lock-in amplifiers.
Up to four tracks of 16-bit, 48 kHz pristine and uncompressed audio can be recorded simultaneously to the 40GB internal hard drive.
In addition, you can bypass the low-pass filter entirely, for a bandwidth of 20 kHz.
The 43 kHz call is generally weak and often inaudible or absent.
Service wanting your accept khz mono becomes the next.