[Vintage-Audio] Re FM Multiplex

[Duane B. Fischer, W8DBF]

Hi All, 	
	
I have here this beautiful contraption called a Teac AN-180. Impressive front
panel! Way cool! Sold for $350 about 1974. I even have the rare calibration
cassette tape too! Yes, even a manual. Seriously cool dudes!				
	
Now this beauty will allow the owner of equipment not having Dolby to both
record and playback in full Dolby. Especially nice if you own a high end Revox
B77 which lacks Dolby! It also appears to allow the owner to use Dolby with FM? 

	
The front panel looks like something from a Space Shuttle console. All sorts of
switches, knobs, meters, lights and so forth. As I said, way cool! But what is
all of this about 'equalization'? No, not the EQ with +/- for different
frequencies. This is a kind of sound equalization, sort of like the bias
adjustment. (a poor comparison)	
	
What does this equalization do here anyhow? There seems to be a relationship to
FM as well as some other devices that can be fed through it.	
	
Wasn't FM broadcast at one time with Dolby? Or am I having a vintage daydream
here? It did not last long, nobody cared and it was quickly gone. So fast, many
never even knew it ever existed.	
	
Hopefully one of you wizards of audio can explain to me what the AN-180 does
besides the Dolby. Thank you.	
	
Duane W8DBF