10.5 Keyboard Lock
With terminals, the most common case of "stop sending" is where the terminal can't keep up with the characters being sent to it and it issues a "stop" to the PC. Another case of this is where someone presses control-S. Much less common is the opposite case where the PC can't keep up with your typing speed and tells the terminal to stop sending. The terminal "locks" its keyboard and a message or light should inform you of this. Anything you type at a locked keyboard is ignored. When the PC catches up on it's work, then the keyboard should unlock. When it doesn't, there is likely some sort of deadlock going on.
Another type of keyboard lock happens when a certain escape sequence (or just the ^O control character for Wyse 60) is sent to the terminal. While the previous type of lock is done by the serial driver, this type of lock is done by the hardware of a real terminal. It's a catch-22 situation if this happens since you can't type any commands to escape out of this lock. Going into setup and resetting might work (but it failed on my Wyse 60 and I had to cycle power to escape). One could also send an "unlock keyboard" escape sequence from another terminal.
The term "locked" is also sometimes used for the common case of where the computer is told to stop sending to a terminal. The keyboard is not locked so that whatever you type goes to the computer. Since the computer can't send anything back to you, characters you type don't display on the screen and it may seem like the keyboard is locked. Scrolling is locked (scroll lock) but the keyboard is not locked.
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