[GreenKeys] Another button question

[Jim Haynes]

Break opens the transmitting signal line for as long as it is held down.

In a manual operation this is a way to interrupt the sending operator.

In the stunt box there will be something which operates on two successive
blank characters and perhaps shorts the keyboard contacts so that station
cannot send.  Or maybe it operates the keyboard lock/unlock mechanism on
a 28.

In Model 15 there is a send-receive-break mechanism with a handle sticking
out the front of the machine on the left side above the keyboard.  In SEND
position the keyboard transmits.  In RECEIVE position the keyboard is 
shorted so it can't transmit.  In BREAK position the keyboard line is
opened to send a break signal.  Then a mechanism on the printer detects
the break signal and flips the switch from SEND to RECEIVE so the sending
operator can't send without resetting the switch to SEND.  Model 28
uses the break key and the keyboard lock and unlock mechanism for the
same purpose.

Break signals are used for other purposes in more automated systems.

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 	"Ya can argue all ya wanna, but it's dif'rent than it was."
 	"No it ain't! No it ain't!  But ya gotta know the territory."
 		Meredith Willson, The Music Man