On Mar 14, 11:53 pm, Mike wrote:
On Fri, 13 Mar 2009 14:57:05 -0700 (PDT), Matty F

wrote:
It could pass up to 100,000 Hz without too
much loss. It was rated at 100 watts. The production version had a
toroidal core of grain-oriented silicon steel. I am the only person
alive who knows why it works at such a high frequency

Because it was used for simultaneous multiple calls with a carrier
group system.

Actually it wasn't. But I was referring to the special core design
which allowed it to pass frequencies of up to 100,000 Hz. I'm no
expert on audio transformers but I'm told that they usually start
dropping off above 20,000 to 30,000 Hz.