[GreenKeys] M28 red keys

[Jim Haynes]

On Sat, 25 Apr 2020, tony.podrasky wrote:
> I had a 28-ASR that had the KBD UNLOCK/LOCK
>
> When the machine received (2?) blank keys
> in a row, it would lock the keyboard.
>
> One explanation I received was the get (you)
> to stop typing because the guy at the receiving
> end had some kind of issue (out of punch tape,
> paper, etc).
Yes, similar to the Model 15 send-receive-break mechanism.  Sending a
break results in two or more blanks in a row, which the M28 stunt
box can detect.  In M15 the switch goes to receive and shorts the
keyboard.  In M28 the keyboard mechanically locks.  Either way the
operator has to quit sending.  Either way it gets the attention of the
sending operator that he needs to quit typing.