Model III BASIC Pokes
Action      Address      Value
Toggle CAPS LOCK      16409      0 = On
Anything Else = Off

Toggle Cursor Blink      16412      0 = Blink
Anything Else = Stationary

Cursor Character      16419      ASCII Value of What You Want

Cassette Speed      16913      0 = 500 Baud
Anything Else = 1500 Baud
The PEEK is actually the ascii value of what you hit

Video Scroll Protect      16916      0-7 = Number of Lines to Scroll Protect

Passing and Getting Values from a USR Call
To return a value to a USR Function Call, load the value into HL and then JP 0A9AH
To keep the value of a USR Function Call, at the beginning of the routine CALL 0A7FH and it will be stored in HL