[QuadList] Slight OT: When did networks transition from 2" Quad to 1" Type C?

[David Perrussel]

Slight off topic question to the group:

Overall, when did the "Big 3" networks (ABC, NBC, CBS and even PBS for 
that matter) start the transition from 2" Quad to 1" Type C or similar 
formats?

I'm sure it was over a period of time, but I'm wondering when the 
transition to 1" really started to get going, pushing out 2" Quad to 
backup status?

For example, when did NBC start to use 1" for the Tonight Show instead 
of 2" Quad?

Also, while I'm on the subject, when did 1" Type C start to end it's 
reign and other formats started to take over?

Thanks!

Dave