Patrick Turner writes:
: DougC wrote:
:
: chapter 23, page 925, halfway down the page they have a list of
: variables and what they signify. They have one capital-R
: subscript-?something? for "valve input resistance at working frequency".
: I can't see what this is, in either the CD or my copy, in either the
: useage in the equation or the definitions. IS this an "i" or a "t"?
:
: It looks like a small t to me.

Agreed. Even under magnification.

: The only bother is that Rt does not appear in the equation
: above the explanation notes, just , R1, R2 & Ro.

It's quite clearly in the equation above that.
For optimum load impedance where µ 1.