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With some portable audio recorders, the output jack is only capable of feeding a line-level signal. Most DSLR and mirrorless cameras have a 3.5m mic input, and plugging a headphone level signal into them is too strong (even when the volume is low). When this is the case, you use an attenuation cable, like a Sescom.
Field mixers typically have a built-in tone generator. The volume level of the tone is equal to the output level of the mixer. If you turn the output level of the mixer up, the tone gets louder, etc.
The idea is that you attach the field recorder to a camera, turn on the tone generator, and then adjust the input level of the camera so that it's getting an optimal audio signal level from the field mixer. Most cameras have a little "hashmark" on their audio level meters that is a visual aid as to where this sweet spot is. The hashmark is usually a little line next to the meter, about two thirds of the way up. (You get bonus points if you take a short break right now and turn on your camera and look for your hashmark).
The new F1 has a tone generator for carrying out this task when you connect to a camera. The sentence that confused you was saying "Hey, you can use a tone generator to get a clean signal from the F1, and you won't need a Sescom cable to do it."
This is a nice feature to have, however, I am curious how clean this output is. The Tascam DR-70D has a dedicated "camera" audio output, and the idea was that it would supply an audio signal that was the right level to connect to a DSLR or mirrorless camera's mic input. The problem was that when you turned that output on the DR-70D low enough to connect to a camera, it got noisy. The sound quality was bad. The solution was to turn that output back up to a louder headphone level, and then to connect an attenuator cable to connect to a camera.
I'm hoping that the F1 will sound good at this lower, camera mic-input level.
Guy - I accept your criticism of my reviews. I suppose you may be right -- but I'm not sold. My reviews are not intensely technical. I tend to lean more toward the impression the equipment gives on a practical level -- rather than how it preforms in a scientific lab.
Jose - I didn't experience a radical difference between the H5 and the H4n. In general, recordings from the H5 sounded slightly better than stuff from the H4n. Is it worth selling your H4n to upgrade? If you're doing this just for sound quality, I don't think it's worth it. If you want a new recorder with new capabilities and new options, then yes.