GTE Telenet and Unix 4.3

[Henry N. Holtzman]

I am about to embark upon getting efficient usage of GTE Telenet and
Unix 4.3.  In particular, I want TELENET to provide the echo when the
terminal is in cooked mode and Unix when it is in cbreak or raw mode.

Has anybody hacked this type of echo control already?  Does anyone
know of a document(s) which detail the protocol I need to use to
switch TELENET in and out of echoing?

Thanks,

-Henry