[GreenKeys] M28 remote keyboard lock - what for?

[Jim Haynes]

On Sun, 4 Dec 2016, Nick England wrote:

> The reason for my message is - what was this used for? In what applications
> was it considered a Good Thing?
> (FWIW, this KSR also includes time-delay, motor-start, and synchronous pulse
> transmission)
> 
What it's for, is similar to the send-receive-break mechanism on the Model 
15.  When two machines are in communication with each other on a wire 
line, such as TWX, the receiving operator can send a break to interrupt
the sending operator.  The break is detected as two consecutive blanks.

In Model 15 the effect is to short the keyboard so it can't send until
reset by the operator, and allows the operator who interrupted to start
typing.  In Model 28 the effect is to physically lock the sender's 
keyboard.

Not useful for much else.