[ProAudio] Western Electric 111C transformers

[Scott Dorsey]

Yes, you could order a 16kc loop line from the phone company as a studio
to transmitter link, or as a link from a local club or used car lot for 
live remotes.  Needless to say the tariff on a 16kc loop line was higher
than for an 8kc loop.

But it wasn't just that.... there were lines carrying FDM multiplexed voice
and data traffic which required wideband circuits, and these were used for
that service too.  

The phone company made millions of these things; they were often available
for the asking if you knew your phone installer well.

Part of the key to these is the core material used, which required a very
large core to prevent saturation at low frequencies but also provided very
low distortion.
--scott